Laminaria japonica, a large perennial brown alga of medicinal and culinary value, thrives in cold marine environments. As a principal economic seaweed species in China, it is characterized by high productivity and exceptional nutritional density. However, the characteristic marine odor substantially compromises consumer sensory acceptance, posing a major constraint on the value-added processing and industrial exploitation of L. japonica-based products. Consequently, the investigation of efficient deodorization techniques and their underlying mechanisms is of considerable importance. The primary odorants of L. japonica are ketones, aldehydes, and alcohols. These volatile compounds can be effectively separated, identified, and quantified using analytical techniques, including gas chromatography-ion mobility spectrometry (GC-IMS), which integrates the superior separation capability of gas chromatography with the rapid detection characteristics of ion mobility spectrometry. This combined technique offers high sensitivity, operational simplicity, and cost-effectiveness and requires minimal sample preparation, making it extensively applicable for the analysis and identification of food flavor compounds. Current deodorization methods for L. japonica include physical, chemical, and biological approaches. Physical methods, such as masking, adsorption, and encapsulation, have limited deodorization efficiency. Chemical methods, including acid-base treatments or antioxidant immersion, although effective, often introduce chemical residues that are difficult to eliminate. Biological deodorization is an environmentally friendly, mild, and efficient approach that utilizes microbial metabolism to convert the odorous substances in L. japonica into non-odorous macromolecules. However, most existing biological deodorization processes use L. japonica pulp or fragments as raw materials, which impedes subsequent refining. This study used whole L. japonica blades for microbial fermentation-based deodorization to establish a superior raw material foundation for downstream processing and address this limitation. To investigate the sources of off-odors in salted L. japonica and the regulatory effects of yeast fermentation on its flavor profile, intact salted L. japonica (without comminution) was used as raw material. Three yeast strains, Pichia kluyveri CICC 32844, Saccharomyces cerevisiae CICC 32883, and Wickerhamomyces anomalus CICC 33313, were selected for fermentative deodorization of both raw and cooked salted L. japonica. The sensory evaluation results indicated minimal and non-significant differences in texture and color among the samples fermented with the three strains. However, significant variations in deodorization efficacy were observed. W. anomalus demonstrated the highest deodorization efficiency and overall performance for raw salted L. japonica, whereas Saccharomyces cerevisiae exhibited optimal deodorization and comprehensive effects on cooked salted L. japonica. W. anomalus and S. cerevisiae were the most suitable strains for raw and cooked salted L. japonica, respectively. The two selected strains were used for flavoring and fermenting salted L. japonica. The volatile flavor compounds in the samples subjected to different treatment conditions were qualitatively and quantitatively analyzed using GC-IMS, enabling characterization of alteration in the flavor profile and comparison with commercial L. japonica products. The relative odds activity value (ROAV) method was used to comprehensively evaluate the flavor characteristics and identify key compounds across different sample groups. The results revealed that the off-odors of salted Laminaria japonica were predominantly attributed to aldehydes and ketones. Among these, 1-octen-3-one was identified as the most potent odor marker, whose mushroom and earthy notes contributed more significantly to the characteristic marine odor than traditionally recognized aldehydes, such as (E)-2-nonenal and propanal. Although thermal processing can generate pyrazine flavor compounds, such as 2,3,5-trimethylpyrazine, via the Maillard reaction, their actual flavor contribution remains minimal (ROAV＜0.1), demonstrating limited masking effects. After fermentative flavoring, the sensory quality of salted L. japonica significantly improved. In raw salted L. japonica, the process generated compounds such as isovaleraldehyde and propyl acetate, which synergistically masked the off-odors. In cooked salted L. japonica, fermentative flavoring produced isovaleraldehyde and alcohols, including n-hexanol, which effectively concealed the marine odor while increasing the diversity of aroma compounds. Comparative flavor analysis of the experimental samples and the identified commercial products identified isovaleraldehyde, phenylacetaldehyde, p-methylbenzaldehyde, 1-octen-3-one, acetylpyrazine, and diallyl disulfide as the key flavor compounds common to all samples. Among these, isovaleraldehyde imparted a distinct chocolate and fatty aroma to L. japonica samples, contributing significantly to their overall flavor profile. Notably, significant differences in overall flavor composition were observed between the experimental and commercial samples. Following the fermentative flavoring treatment, 1-octen-3-one was no longer the dominant contributor to the flavor profile, demonstrating the feasibility and effectiveness of the fermentation-based flavor modulation process developed in this study.In this study, qualitative and quantitative analyses of the key flavor compounds in raw salted L. japonica and its seasoned or fermented derivatives were performed. By systematically investigating compositional differences and dynamic changes in volatile profiles before and after yeast-mediated fermentation, and by comparing them with commercial products, L. japonica products with distinctive flavor characteristics were successfully developed. This study reveals the dynamic transformation of flavor compounds during microbial fermentation, and offers novel strategic insights for the development of seaweed products and the optimization of microbial deodorization technologies.