Objective To observe the histological structure of skin in SD rat at different stages. Method By using 10 percent formaldehyde paraffin section, and staining with hematoxylin and eosin. Result The skin thickness was thin in SD rat which lacked sratum lucidum at day 1. They had a few shallower and irregularly positioned hair follicles and well-developed sebaceous glands. The skin hair follicle size increased significantly, An increase in thickness of the epidermis was observed in SD rat as a result of an increase in the number of cell layers in basal layers and stratum corneum, Hair follicles had moved down to the subdermal fat tissue layer at month 6. Analoisis in sebaceous glands and sweat gland were observed in SD rat with very thin elastic fibers at month 24. Conclusion Histological structure through the skin of SD rat at different stages showed difference.