Objective To investigate the numbers of corpus luteum and ovarian follicles and compare the levels of serum prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E₂) in different phases of estrus cycle in female gerbils. Methods Consecutively taking vaginal smears of the gerbils and directly examined under light microscope to distinguish the four phases of the estrus cycle. Hematoxylin and eosin staining was used to histological examination of the gerbil ovaries, and to detect the levels of serum PRL, LH, FSH and E₂ by ELISA assay during estrus cycle. Results The proportion of cornified vaginal exfolliated cells could be the basis to distinguish four phases respectively: proestrus, oestrus, metoestrus, and dioestrus. Moreover, there were no significant differences between the numbers of ovarian follicles in different phases of estrus cycle. The numbers of corpus luteum in preoestrus were significantly lower than that in the other phases of estrus cycle (P<0.05). The levels of serum PRL and LH were increasing constantly from preoestrus to dioestrus, and both reached a peak at dioestrus (P<0.05). The levels of serum FSH and E₂ both peaked at preoestrus, and were significantly higher than those at oestrus, metoestrus and dioestrus (P<0.05). Conclusions There are no significant differences between the numbers of ovarian follicles in different phases of estrus cycle. Gonadotropin, prolactin and estradiol paly important roles in the regulation of estrous cycle. The phases during which surges of FSH and E₂ occur in Mongolian gerbils are similar to those of rats and mice, while the PRL and LH are different. Our findings provide further reference to the study of reproductive physiology of Mongolian gerbils.