Objective To explore the histopathological characterization of the female beagle dog's uterus in drug safety assessment. Methods\ As controls in studies performed at our laboratory to assess the drug safety, female beagle dogs aged 43-74 weeks were at random divided into four groups and eight in each group were killed in spring, summer, autumn and winter respectively. The histological structures of their uteri were analysed. Results\ Oestrus\|related changes in the histological structure of uterus and weight were observed. The differences between the uterus of the four groups, especially in uterus endomertrium and uterus glands, showed highly comparative medicine significance in drug safety studies. Conclusion\ The results suggested that when non\|pregnancy female beagle dogs were used in safety assessment studies, the toxicologic pathology evaluation of uterus should be correlated with the physiological factors of distinguishing spontaneous changes.\;