Argopecten irradians were stimulated by injection with β-1,3-glucan and its carboxylmethyl-glucan （CMG） with different degrees of substitution （DS） （ including CMG 1, CMG 2, CMG 3 and CMG 4 with DS of 0. 335, 0. 556, 0. 732 and 0. 857, respectively）. The immunological stimulation aclivity of β- 1,3-glucan and CMG was compared by determining the contents of the serum protein and phenoloxidase （PO）, superoxide dismutase （SOD）, lysozyme （LSZ） activity in the serum and blood corpuscle of Argopecten irradian after injection for 24, 48 and 72 h, respectively. The results showed as follows： 1 ） Compared with the control, the serum protein contents had no significant differences in Argopecten irradians injected with β-1,3-glucan. After injection for 48 h, the serum protein contents in group CMG 2, CMG 3 and CMG 4 were significantly higher than those in the control. 2）β-1,3-glucan and CMG 4 could quickly enhance the PO activity in the serum. The bigger DS of CMG , the higher immunological stimulation activity on the PO activity in the blood corpuscle. 3） CMG 4 group was more effective on adding the SOD activity in the serum and blood corpuscle of Argopecten irradiand 4） After injection with CMG 4 for 24 h and 48 h, the LSZ activity in the serum was very significantly higher and higher than that in the control respectively, but there were no significant differences in each treatment at 72 h after injection. As far as the LSZ activity in the blood corpuscle, CMG 3 group was very significantly higher than that in the control at 24 h after injection, and CMG 4 group was significantly higher at 24, 48, 72 h after injection. The results indicated that carboxylmethyl modification could not only enhance the water-solubility of β- 1,3-glucan, but also affect the immunological function. CMG 4 with DS of 0.857 had the most obvious effect on the immunological function in Argopecten irradians.