Abstract: To analyze the genetic rule of allometry between body weight and morphological traits for Japanese flounder (Paralichthys olivaceus), we established 19 full-sib families by artificial insemination to observe their body weights and morphological traits at different days of age. We constructed the optimal joint allometry model by stepwise regression method which was then nested into the fixed and genetic effects of animal model for body weight. Furthermore, we analyzed the genetic rules of allometry for multiple morphological traits. The allometric index between body weight and total length presented positive allometry with maximum value of 1.415 5. The allometric index between residual morphological traits and body weight ranged from 0.061 5 to 0.718 0, showing negative allometry. The maximum positive genetic correlation of allometric index between total length and caudal peduncle depth reached 0.907 8, while the highest negative genetic correlation existed between total length and caudal peduncle length (-0.946 8). Comparing different models by the statistic criteria, Model Ⅰ is the optimal regression model for dynamic allometric analysis.