Diazepam is a long-acting benzodiazepine sedative primarily used clinically for treating anxiety, insomnia, epilepsy, and other conditions. It works mainly by enhancing the effect of the γ-aminobutyric acid (GABA) neurotransmitter to inhibit central nervous system activity, thereby producing various pharmacological effects such as sedation, hypnosis, anticonvulsant action, and central muscle relaxation. Prolonged or improper use of diazepam may cause adverse reactions including drowsiness, headaches, auditory hallucinations, and impose a burden on the liver. In newborns, it may even lead to long-term cognitive impairment due to its ability to cross the placental and blood-brain barriers. Diazepam is classified as a Schedule II psychotropic substance in China and has not been approved as a veterinary drug for aquaculture. GB 31650—2019 "National Food Safety Standard - Maximum Residue Limits for Veterinary Drugs in Foods" explicitly stipulates that diazepam shall not be detected in animal-derived food products, reflecting strict regulatory control over its presence in the food chain. However, diazepam has been occasionally detected in freshwater aquatic products such as grass carp, crucian carp, and common carp, raising concerns about food safety and public health. The contamination sources of DZP residues in aquatic products may originate from water pollution or input materials, with the issue of DZP residues caused by fishing baits being particularly prominent. Some scholars have found through simulated aquaculture environment medicated bath exposure that DZP has a relatively long metabolic cycle in aquatic products, requiring an extended withdrawal period to ensure the quality and safety of aquatic products. Accumulation is particularly evident in metabolically active tissues such as the liver and kidneys, where biotransformation occurs. However, research on residual metabolic risks introduced through bait remains relatively limited. To address this gap, Cyprinus carpio were selected as the research subjects and were orally administered bait containing diazepam (DZP). Tissue samples, including skin muscle, plasma, gills, liver, and kidneys, were collected at scheduled intervals from 1 hour to 288 hours post administration. High-performance liquid chromatography-tandem high-resolution mass spectrometry was employed to detect the residues of DZP and its metabolites—nordazepam (NZP), temazepam (TZP), and oxazepam (OZP) in various tissues. This study investigated the distribution and metabolic patterns of DZP and its metabolite residues in Cyprinus carpio following the ingestion of DZP-containing bait to assess the absorption, distribution, metabolism, and elimination dynamics of DZP. The results indicated that at 18°C, after a single oral administration of feed containing 3 mg/kg and 30 mg/kg DZP to Cyprinus carpio, DZP rapidly accumulated in their bodies and reached high residual levels. The residue distribution exhibited distinct tissue specificity: within 48 hours, DZP concentrations in the liver and gills decreased significantly, suggesting these metabolic and respiratory organs possess strong clearance capabilities. In contrast, residual concentrations remained high in edible tissues such as skin muscle, reflecting strong accumulation tendency of DZP in lipid-rich tissues. The primary metabolites of DZP were OZP and NZP. It is noteworthy that the time required for DZP in edible tissues to decrease to the detection limit (0.5 μg/kg) was relatively long, indicating its prolonged elimination half-life. In order to evaluate the effect of different cooking methods on the reduction of DZP residues, the effects of steaming and frying cooking methods on the elimination of DZP residues in edible skin and muscle tissue of carp were carried out at different times. The results demonstrated that during the initial frying stage, the dominant mechanism was the transfer of DZP to the cooking medium, while in later stages, thermal-induced conversion to OZP became the primary pathway, a process closely related to its solubility and thermal sensitivity. Based on the residual levels of DZP in the edible skin and muscle tissues of Cyprinus carpio under experimental exposure concentrations, a dietary intake risk assessment was conducted in conjunction with the Acceptable Daily Intake (ADI) value. The results indicated that the dietary exposure risk of DZP in the edible skin muscle tissues of Cyprinus carpio under experimental conditions was at an acceptable level. The residual dietary intake risk introduced by the extremely high-concentration DZP bait still requires attention to avoid potential harm to human health. This study systematically reveals the residual dynamics and transformation mechanisms of DZP in Cyprinus carpio, providing data support for the scientific evaluation of DZP risks introduced through feed and establishes a scientific foundation for formulating relevant regulatory strategies to ensure aquatic product quality and consumer health.