OBJECTIVE To study the anti-hyperglycemic effective sites of crude polysaccharides from Mactra veneriformis (MVPS).METHODS Hyperglycemia models were established by intravenous injection of alloxan via tail vein of ICR mice under a dose of 80 mg/kg.After 96 h,mice with fasting blood glucose levels≥11.1 mmol/L were chosen and divided into groups.MVPS 1 treated at the doses of 200,400,800 mg/kg and 1 200 mg/kg once daily,respectively.At 7th and 14th days, respectively,the levels of blood glucose,GSP,TCH and TG were measured.Other diabetic mice were divided into MVPS 1 (800 mg/kg),MVPS 2 (180,360 mg/kg) and MVPS 3 (2 040 mg/kg) groups.After 7 d treatment,both body weights and fasting blood glucose levels were measured.RESULTS MVPS 1 of 800 mg/kg displayed the optimal anti-hyperglycemic effect on diabetic mice and reduced GSP,TCH and TG levels of diabetic mice;MVPS 2 showed significantly anti-hyperglycemic ac-tivities,compared to the model group.MVPS 3 exhibited no anti-hyperglycemic activities.CONCLUSION MVPS 1 displays the optimal hypoglycemic effect at the dose of 800 mg/kg,and its hypoglycemic active site focuses on MVPS 2.