Breeding new varieties is a main approach to prevent the genetic degradation and improve traits for the purpose of economic benefits. Quantitative genetics evaluation is one of the main methods used in Japanese flounder (Paralichthys olivaceus) breeding. By using the core populations from the established breeding program, this research evaluated three growth related traits (body weight, total length, and body width) among 42 newly-generated families on 140 d, 170 d, 200 d (before mixing pool) and 380 d (after mixing pool). The quantitative genetic analysis was carried out using MINQUE, REML and BLUP. The results showed that the variation coefficient of growth traits ranged between 10.56% and 38.62% at different day age. Among three growth traits, the variation coefficient was the largest in body weight, and was relatively small in total length and body width. The variation coefficient of different traits decreased with the increase of day age. The additive variance component ratio for the three traits was between (0.13±0.01) and (0.29±0.06), whereas the random variance component ratio was between (0.71±0.06) and (0.87±0.01). By contrast, the narrow sense heritability ranged between (0.13±0.01) and (0.29±0.06) and the generalized heritability was from (0.15±0.01) to (0.54±0.06). All of the above genetic traits were highly significant (P<0.01). Comparison of genetic effects on three growth traits during different developmental stages revealed that four parental groups (F0990, F1005, KS, and F0719) showed significant positive effects, whereas six groups of parental groups (F0751, F0768, F0780, F09121, F0927, and RS) showed significant negative effect (P<0.01). By contrast, the rest of 32 parental samples showed no significant effect. The correlation coefficient was between 0.82 and 0.96 in phenotype and between 0.72 and 0.97 in genotype. The phenotypic and genetic correlation coefficient of different day ages were maintained at a relatively stable level. Breeding value of the 380-day age was estimated using the BLUP method. The results showed that breeding value of the parental fish body weight was between 14.63 and 100.05. Among all the families, the highest breeding values for body weight were found in F1005-8, F09119-11, F09125-4, F0915-57, F09104-12, F1264, F0908-38, F0927-20, F1005-53, F0990-6, F09125-7, F0751-14 and F1005-42, average between 20.87 and 35.60. The families with the highest average weight breeding value were F1416, F1428, F1442, F1418, F1427, F1408，F1402, F1412 and F1446. Compared with the method of phenotypic selection, the breeding values obtained from growth-based selection were better for improving growth traits since the selection efficiency was up to 81.91%. In this study, parents and families with superior growth traits were selected to improve the genetic quality and new varieties of P. olivaceus. Meanwhile, it provides an important theoretical basis for the development of P. olivaceus breeding program.