Abstract: In order to elucidate the effects of the morphological traits on body weight of S. intermedius at different ages, in the report, the shell diameter, shell height, diameter of the peristome, maximum width of the ambulacrum, maximum width of the interambulacrum, and body weight of S. intermedius were measured, the correlations between the morphological traits and body weight were systematically analyzed. The path analysis, multiple regression, and allometric growth modeling were used to analyze the inter-trait relationships and the effects of morphological trait of S. intermedius on body weight. The results indicated that the correlations among all measured traits in S. intermedius across four developmental stages (10, 16, 22, and 28 months of age) were very significant (P<0.01). The effect of the shell diameter on the body weight of S. intermedius at each month of age was the biggest. The stepwise regression method was used to construct the multiple regression equations for the body weight and morphological traits of sea urchins at each month of age. The growth parameters of 10~28-month-old S. intermedius were higher than 1, which suggested that they were in the allometric growth stage (positive allogenesis). With the increase of the age of sea urchins, the effects of the various morphological traits on body weight changed, among which the effect of the shell diameter on body weight of sea urchins increased first and then decreased, and the effects of the other morphological traits on body weight gradually increased with the increase of sea urchins’ age at months.For 10～28-month-old sea urchins, the biggest morphological trait was shell diameter, which can be used as the main selective trait in the breeding process. Other morphological traits, including shell height and diameter of the peristome, can be used as auxiliary selective traits.