Objective To investigate the method to establish type I diabetic rat models induced by streptozotocin(STZ) and observe the stability of diabetic changes in rats of different sex.Methods STZ was injectied intraperitoneally for once.To measure and statistically analyze the fasting blood glucose level,body weight,water intake,insulin and c-peptide of the rats at different time points.Results The blood glucose level reached the mold-guide standard and diabetic appearance occurred at 3 days after STZ administration.The fasting blood glucose level became stable since 14 days after STZ injection in male rats,which were kept under observation for 16 weeks.All the male rats met the mold-guide standard.While,the fasting blood glucose level in the female rats met the mold-guide standard and keep stable since 4 weeks after STZ injection.Conclusion So far,intraperitoneal injection of STZ is an excellent method to induce type I diabetes in rats.However,the stability of fasting blood glucose level is differently related with the sex of animals.It is stable from 14 days after SYZ injection in male rats,but 4 weeks in female rats.