In order to find out the correlation among the quantitative characters and influencing factors of production of Macridiscus multifarius, high phenotypic traits shell length (SL), shell height (SH), shell width (SW), body mass (BM) of randomly selected different geographic groups of wild equilateral shallow clam in Zhoushan, Zhejiang Province were measured, and relationship between morphological traits and weight traits of M. multifarius was analyzed by path analysis. The results showed that the effects of morphological traits on body mass were different between the two populations, and shell height had the greatest influence on body mass in Shengsi population, while shell width was the most influential trait on body mass in Putuo population. The correlation coefficients between morphological traits and body mass of the two populations were great and with extremely significant correlation. The indirect action of morphological traits on body mass was greater than the direct action. The regression equations of variables with significant partial regression coefficients for body mass were expressed as Y=0.505X₁ + 0.773X₂ + 0.723X₃-41.313, Y =0.258X₁ + 0.432X₂ + 0.888X₃ -23.607, where Y represents body mass, X₁, X₂ and X₃ represent shell length, shell height and shell width, respectively. The regression coefficients of the two equations are extremely significant. The results showed that the shell height of Shengsi population was an ideal index to measure the body weight in the breeding of the equilateral shallow clam, while the shell width of Putuo population should be paid attention to, and this may provide a theoretical basis for the breeding of M. multifarious.