Abstract: Garlic (Allium sativum) is belonging to Alleacea family. This plant has anti microbial, anti cancer properties because of its organosulfuric compounds. In this research, effect of hydro-alcoholic extract of garlic was studied on reproduction system of female mice (Balb/C). At first, samples were divided in 5 groups with 10 members: 1 group as control, 3 groups received treatments and 1 group received placebo. Samples were kept in same places. For synchronizing estrous cycles of rats, cloprostenol and progesterone were injected in their peritoneum with a 3 days interval. Hydro-alcoholic extract of garlic was prepared in 3 doses (50,100 and 200 mg kg-1) and was injected in peritoneum for 20 days. Control group was not injected and placebo group was injected using physiological serum. After 10 injections, samples bloods were analyzed for FSH, LH, estrogen and progesterone using RIA method. Results showed significant reduction in FSH and LH levels and significant increase in estrogen and progesterone levels. According to results of this study, hydro-alcoholic extract of garlic has a negative effect on female reproduction system in all various doses (50,100 and 200 mg kg-1).