PURPOSE: To investigate the influence of aerobic exercise in rats with polycystic ovary syndrome (PCOS). METHODS: 32 23-day-old SD female rats were randomly assigned into 4 groups, i.e. normal control group (NC, n=8), exercise control group (EC, n=8), PCOS control group (PC, n=8) and PCOS exercise group (PE, n=8). PC group and PE group were modeled by injecting DHEA. EC group and PE group simultaneously implemented Masashi exercise intervention (unloaded free swimming, 20 min/time, 6 d/week for 15 d). Measure the serum testosterone (T), estradiol (E2), follicle-stimulating hormone (FSH) and leptin (LP) of rats by ELISA. Observe ovarian histological changes through the hematoxylin-eosin stain, the P450arom expression (optical density, OD) in ovarian by immunohistochemistry. RESULTS: There were obvious cystic dilated follicles in the ovarian tissue of the PC group, and compared with the, there are many normal follicles in the ovary of the PE group. The PC group exhibited a higher serum level of FSH, T, E2 and the P450arom expression in ovarian than NC group (P < 0.05). Compare with the PC group, the serum level of LP, T, E2 were decreased in the PE group (P < 0.05). However, compared with the NC group, the EC group showed no difference in the serum level of FSH, T, E2, and the P450arom expression in ovarian (P > 0.05). Besides, the PE and PC group showed no difference in the serum level of FSH and the P450arom expression in ovarian (P > 0.05). The serum LP level in rats was positively correlated with T (r=0.893), E2 (r=0.612), FSH (r=0.620) level and the P450arom expression(r=0.501) in ovarian. CONCLUSION: Aerobic exercise can reduce the LP levels of PCOS rats, relieve leptin resistance, alleviate high estrogen blood disease and abnormal P450arom expression in ovarian, but cannot eliminate the sex hormone disorder. The Changes of T, FSH, E2, LP, And OD among 4 groups(x ̅±SD)