Abstract: To study the effect of sturgeon chondroitin sulfate (ChS) on immune organs of m ice，the mice were administered with the different doses of sturgeon chondroitin sulfate. After two weeks， the thymus and spleens were collected by surgical operation and were weighed，then were processed by being fixed in Calot’s ，paraffin embedded，made slice and modified toluidine blue (M T B ) staining. The distribution and number of mast cells of mouse were observed by looking through a microscope. The results were showed that the different doses of sturgeon chondroitin sulfate could enhance the weight of the immune organ and increase the number of mast cell in the immune organ of m ice，among w hich，administered with the dose of 600 m g/kg could enhance significantly the weight of the thymus(P<0.05) and increase the number of the mast cells in the thymus(P<0.01)，and administered with the dose of 60 m g/kg could enhance significantly the weight of the spleen (P<0.01) . Only administered with the dose of 6m g/kg could increase the number of the mast cells in the spleen evidently (P<0.01）.