Objective To observe the different cell surface characteristics of the breast carcinoma in closed breeding Microtus fortis and Kumming mouse.Method Tissues were observed under the scanning electron microscope. Results There were a number of folds and very small irregular popular processes on the surface of normal mammary gland cells of Microtus fortis ;while the surface of breast carcinoma cell in Microtus fortis was densely covered with a large number of long and irregular microvilli. In Kunming mouse, the cell surface of its breast carcinoma was also covered with microvilli, whose morphologic characteristics were very distinct and the end of them was round in shape. Conclusion There are distinguishing characteristics of microvilli on the surface of the breast carcinoma cells between Microfus fortis and Kunming mouse.