Objective To observe the preventing effect of intraocular injection of Bevacizumab (Avastin) to retinal microvascular proliferation in non-obese diabetes mice. Methods In the study, thirty non-obese diabetes mice (NOD mice) were selected. The left eyes of mice were selected as treatment group with 1mu;l A vastin (25mg/1ml) injected, and right eyes were selected as control group with 1 mu;l saline injected. One week, one month, two months after injection, ten mice were selected randomly, and then enucleated two eyes, in which the retinal microvascular endothelial cells ultrastructure and immunohistochemistry of retinal CD34 and VEGF, were observed and measured. The differences of dense of positive sta ining between two groups were compared by digital image analysis. Results The positive expression of VEGF and CD34 were brown staining, and the positive staining of CD34 located in vascular endothelial cells. There was statistically significant difference in VEGF expression between two groups in 1 week and 1 month after injection（t=21.6, t=13.5; P＜0.01), and no statistically significant difference in 2 months after injection （t=0.9, P＞0.05）. There was statistically significant difference in CD34 expression between two groups in 1 month and 2 months af ter injection（t=3.2, P＜0.01; t=2.7, P＜0.05） and no statistically significant difference in 1 week after injection（t=1.3, P＞0.05）. In every time point after injection, there was no obvious change in the microstructure of retinal vascular endothelial cells. Conclusion Intraocular injection of Avastin could prevent the abnormal proliferation of retinal microvascular in NOD mice. （Chin J Ocul Fundus Dis，2008，24：180-183）