Objective To study whether the long term use of glucosamine sulfate is harmful to people. Methods Eighty SD rats were divided randomly into 4 groups by body weight, with 10 male rats and 10 female rats in each group. Then rats were fed with glucosamine sulfate at the dosage of 0, 0.75, 1.5 and 3.0g/kg for 30 days, and were weighted once every week. Blood samples from eyeballs were collected for blood routine test and biochemical indexes. Liver, kidney, spleen and stomach of rats were weighted and used for histopathological examination. Results The weight gain of rats in all treated groups was similar to that in non-treated group. Hb, RBC, WBC and leucocyte differential count of rats in all treated groups were normal. AST, ALT, BUN, Cr, TC, TG, Glu, Alb and TP of rats in all treated groups were normal. Kidney/body, spleen/body, liver/body and testicle/body coefficients of rats in all treated groups were similar to those in non-treated group. No pathological changes in liver, kidney, stomach and spleen of rats in all treated groups were observed under microscope. Conclusion No adverse effect was observed in rats fed with glucosamine sulfate for 30 days, which indicate that long term use of glucosamine sulfate might be safe for people.