Abstract: Fifty individuals were randomly selected from the four instar in the wild populations of Mya arenaria Dalian Lushun Longwangtang waters.And then,the measurement of shell length(X₁),shell height(X₂),shell width(X₃) and weight(Y₁),the shape of living body weight and soft body weight(Y₂) were performed,while correlation coefficient between characters was also calculated.The effects of phenotypic traits on weight traits were analyzed by means of correlation and path analysis.The results showed that the correlation between the 5 quantitative traits reached significant level(P<0.05).The correlation coefficient was from 0.676 to 0.931.Phenotypic traits had the same effect on living body weight and soft body weight.The largest of the two direct effects were shell length,while their values were 31.80% and 23.90%,respectively.The largest indirect effects of the two were shell width,while their values were 10.80% and 8.40%,respectively,and shell height was the least.Multiple regression analysis was established for the regression equations of shell length(X₁),shell height(X₂),shell width(X₃) with 3 estimates of living body weight(Y₁) and soft body weight(Y₂) as:Y₁=1.421X₁ + 1.563X₂ + 0.722X₃ -125.360 and Y₂=0.348X₁ + 0.390X₂ + 0.169X₃-28.119.The results provided a theoretical basis for Mya arenaria selective breeding:in order to improve the living body weight or soft body weight,the shell length was the main consideration,while strengthen the coordination of shell width should be also considered.