Objective To investigate the morphological changes in the ovaries and the serum levels of several related hormones, insulin and glucose in the polycystic ovary syndrome ( PCOS) mouse model induced by D-galactose, and to discuss the significance. Methods 20-week-old female ICR mice were injected daily (i. p) with D-galactose for up to 8 weeks. ELISA was used to measure the serum levels of follicle-stimulating hormone (FSH), estrogen (E2), testosterone (T) and insulin (INS). HE staining was used to examine the morphological changes of the ovaries. The stages of the estrous cycle were verified by vaginal cytology. Results The ovaries of the D-galactose-treated mice showed almost polycystic changes with ovary cysts and atretic follicles. Abnormal estrous cycles were induced in D-galactose-treated mice. Comparing with the normal group, the serum estrogen (E2) and testosterone (T) were increased and the serum FSH was reduced in D-galactose group, with a statistically significant difference (P <0.001 or P<0.0001). The level of serum insulin was significantly higher in the D-galactose-treated mice than in the normal group (P < 0.01). In comparison with the normal group, the value of 1/ (INS×G) was significantly decreased in the D-galactose-treated mice (P < 0.05). Conclusions The level of serum sex hormones and the ovarian morphology of the D-galactose-treated mice were similar to those of the patients with PCOS, and insulin resistance was observed. Our results indicate that the D-galactose-treated mouse model may be a useful animal model for the future experimental research of polycystic ovary syndrome.