Objective To study the effects of PM_2.5 on reproductive hormone levels and pregnancy outcome in female rats. Methods Thirty healthy 4-week old female Sprague-Dawley rats were randomly divided into the control group (normal saline), low dose of PM_2.5(1.5 mg/kg) group and high dose of PM_2.5 (37.5 mg/kg) group. After the blood samples were collected, the animals were exposed to PM_2.5for 10 days, and then the rats were mated. On the 19^th day of pregnancy, the rats were sacrificed for pregnancy outcome observation and blood samples were collected for hormone test. The blood hormone levels were detected using an ELISA kit. Results The live fetus rates in the control, low dose PM_2.5 and high dose PM_2.5 groups were 90.77%, 59.49% and 60.27%, respectively (P<0.05). The live fetus rates in the low dose PM_2.5 and high dose PM2.5 groups were significantly lower than that in the control group (P<0.05). PM_2.5 decreased the levels of E2, PROG, CG and LH (P<0.05), compared with that in the control group. Although the blood levels of FSH were not significantly different between the low dose and control groups (P>0.05), the level of FSH in the high dose group was significantly decreased (P<0.05). Conclusions PM_2.5may affect pregnancy outcome through influencing the hormone levels.