123 clams Mactra veneriformis Reeve were randomly sampled in April 2010.The shell length(X₁),height(X₂),width(X₃),and the live body weight(Y)and edible tissue weight(Z)were measured.The shell morphological traits were used as independent variables,and live body weight or edible tissue weight used as a dependent variable for calculating the path coefficients,correlation index and determinant coefficients.The direct and indirect effects of all shell morphological traits on weight traits were analyzed and a multiple regression equation was obtained.The results showed that the live body weight and edible tissue weight were significantly correlated with the three shell morphological traits(P<0.01).The direct effects of three shell morphological traits on live body weight and edible tissue weight were in order of shell widths>shell lengths>shell heights.Shell width had greatest direct effect on the live body weight and was the key influencing factor.The determinant coefficients of shell width on live body weight and edible tissue weight were 0.302 5 and 0.224 7.The multiple regression equations were obtained to estimate live body weight and edible tissue weight as Y=-19.537+0.244X₁+0.266X₂+0.732; Z=-2.456+0.035X₁+0.035X₂+0.089X₃.This study shows in selective breeding of M.veneriformis Reeve the shell width was the ideal measurement index.The results provide a theoretical basis for breeding of M.veneriformis Reeve.