To explore the main morphological traits driving the development of body mass and the differences among populations, we randomly sampled 131 Conger myriaster individuals from four geographical populations (Dalian, Weihai, Rushan and Qingdao) along the Yellow Sea and the Bohai Sea of China. Body mass (Y) and eleven morphological traits (total length (X₁), tail length (X₂), snout-vent length (X₃), length before the first dorsal fin (X₄), trunk length (X₅), head length (X₆), head width (X₇), snout length (X₈), eye length (X₉), eye distance (X₁₀) and the head length behind the eye (X₁₁)) were measured, and their relationships were analyzed by correlation analysis, multiple regression analysis, path analysis, and grey relational analysis. The results showed that the coefficient of variation of body mass (Y) was the largest, indicating great potential for genetic improvement. Four morphological traits (X₁, X₃, X₁₀ and X₁₁) were significantly correlated with body mass as indicated by the path coefficients (P<0.01). The optimal multivariate linear equation for each population was as follows: Y_Dalian=-119.682+1.468X₁, Y_Weihai=-116.838+1.117X₃+2.971X₁₀, Y_Rushan=-142.089+7.663X₁-2.399X₁₁, Y_Qingdao=-107.977+4.770X₁. The grey correlations between 11 morphological traits and body mass ranged from 0.598 to 0.830. The grey relational grades of five morphological traits (X₁, X₂, X₃, X₅ and X₈) to body mass were much higher than those of other traits, which were inconsistent with the results of path analysis. Total length (X₁) and snout-vent length (X₃) were the main factors affecting body mass, which should be used as the dominant selection traits during the genetic breeding.