Abstract： Objective To analyse the risk factors of the postoperative iris neovascularization(INV) of proliferative diabetic retinopathy(PDR) patients treated by vitreoretinal surgeries.(Methods) The postoperative INV was analysed in 451 PDR patients(536 eyes) after vitretomy.Risk factors were studied using multivariate logistic regression analysis. Results INV developed in 44 eyes(8.2%) and neovascluar glaucoma(NVG) occurred in 12 eyes(2.2%).The INV occurred most often in the course from 1 month to half a year after surgery.Logistic regression analysis showed that significant risk factors were preexisted INV and postoperative retinal detachment after the first vitrectomy(P<0.001).The INV rates of different stage of PDR eyes were approximate in each other(Ⅳ:8.5%,Ⅴ:6.1%,Ⅵ:9.0%).In the eyes treated by panretinal coagulation(PRP) before surgery,the INV rate was lower(6.2% vs 9.9%).In the patients who retained themselves′ lens,the postoperative INV rate was lowest(6.8%),with no statistical difference compared with intraocular lens group(8.9%).Conclusion The preexisted INV and postoperative retinal detachment after the first vitrectomy are major risk factors for postoperative INV.It seems that there is no obvious correlation(between) the severe stage of PDR and postoperative INV occurrence.