To study the hypoglycemic effect of hydrolysate of Porphyra haitanensis on diabetes, the hyperglycemia mice were induced by alloxan to analyze the effects of HPH on weight, organ coefficient, glucose tolerance, serum insulin (INS), glycosylated serum protein (GSP), liver glycogen and so on. The result showed that the growth of weight, spleen coefficient, INS and concentration of liver glycogen in the mice were raised at certain doses of HPH, while liver coefficient and GSP were lower, but thymus coefficient remained steady. Among them, the blood glucose level of the mice treated with high and medium dose HPH were stable and were significantly lower than the control. In conclusion, HPH has obvious hypoglycemic effect on hyperglycemia mice induced by alloxan.