Abstract： Objective To observe the the inhibitory effect of recombined adenovirus mediated delivery of p21 (rAd-p21) on oxygen-induced retinal neovascularization in mice.Methods A total of 56 C57BL/6 mice at the age of seven days were divided into control group,phosphate buffer solution (PBS) group,rAdp21 group and rAd-no purpose gene control (rAd-NC) group,14 mice in each group.The retinal neovascularization of PBS,rAd-p21and rAd-NC group were induced by oxygen,and received an intravitreal injection 1 μl PBS,rAd-p21 and rAd-NC at postnatal day 11,respectively.The rats of control group were not intervened.At postnatal day 17,RNV was determined by retinal flat mounts and retinal section; nonperfusion areas of retina were analyzed by Image-Pro plus 6.0 software; reverse transcription-polymerase chain reaction (RT-PCR) and Western blot was used to measure the mRNA and protein expression of p21 and CDK2.Results Compared with PBS and rAd-NC groups,the retinal non-perfusion areas,neovascularization and the numbers of endothelial cell nuclei breaking through the internal limiting membrane in rAd-p21 group were reduced significantly.Non-perfusion areas of retina in rAd-p21 group was less than that in PBS and rAd-NC groups,the difference among these three groups was significantly (F＝ 101.634,P＜0.05).Compared with the other three groups,the level of p21 mRNA and protein in rAd-p21 group increased significantly (F=839.664,509.817; P＜0.05) ; the level of CDK2 mRNA and protein in rAd-p21 group decreased significantly (F=301.858,592.882; P＜0.05).Conclusion rAd-p21can inhibit oxygen-induced retinal neovascularization,up-regulated p21 expression and down-regulated CDK2 expression may be the mechanism.