Abstract: In order to explore the change rules of vaginal cells at different stages of estrous cycle in healthy and repeatedly infertile Simmental cattle, eighty female Simmental cattle and nineteen repeated infertility Simmental cattle were randomly selected as experimental animals according to their age of 3-5 years, body weight of 500-700 kg, normal growth and development, moderate fat, and health. Each cattle was intramuscularly injected with 3 mL Cloprostenol Sodium injection. The vaginal contents of Simmental cattle were collected, smears and giemsa staining were performed. The morphology of vaginal epithelial cells of healthy and repeated infertility Simmental cattle were observed by microscope, the proportion of different types of cells was counted, and the morphological characteristics of cells in different stages of estrous cycle were analyzed. The result showed that there were mainly nuclear epithelial cells, keratinized epithelial cells, leukocytes and cell fragments in the vaginal smears from healthy and repeated infertile Simmental cattle. In the proestrus, the proportion of nucleated epithelial cells in healthy and repeated infertile Simmental cattle was 48.79% and 54.77%, respectively, which was significantly higher than that of other cells（ P＜0.05）. The proportion of keratinocytes in the estrus was 48.26% and 41.62%, respectively, which was significantly higher than that of other cells（P＜0.05）. The proportion of leukocytes in the late estrus was 48.11% and 54.55%, respectively, which was significantly higher than that of other cells（P＜0.05）. The proportion of leukocytes in the diestrus was 42.43% and 52.14%, respectively, which was significantly higher than that of other cells（P＜0.05）. There was no significant difference in the proportion of different types of epithelial cells in different stages of estrus cycle between healthy and repeated infertile Simmental cattle（P＞0.05）. The morphological change characteristics of vaginal cells were consistent with the proportion characteristics of vaginal cells. The results indicated that the proportion of nucleated epithelial cells in the proestrus was the highest in healthy and infertile Simmental cattle; keratinized epithelial cells dominated in the estrus, and leukocytes were the most significant in the late estrus and the dioestrus. The different stages of estrous cycle of healthy and repeated infertile Simmental cattle can be distinguished according to the change characteristics of vaginal cell types and the proportion of various types of cells in the smear, so as to determine the optimal insemination time.