Objective: To investigate the effects of the timing of a preoperative intravitreal injection of Conbercept on the expression of vascular endothelial growth factor (VEGF) and the recovery of visual acuity in patients with diabetic retinopathy (DR). Methods: In this prospective clinical study, 109 patients with DR treated in the People's Hospital of Kaizhou District, Chongqing, from May 2015 to May 2017 were randomly divided into A, B and C groups, 32 patients in group A, 43 patients in group B, 34 patients in group C.The three groups were treated by vitrectomy. Patients in group A were not treated with an intravitreal injection of Conbercept before surgery, patients in group B were treated with an intravitreal injection of Conbercept at 3 d before surgery, and patients in group C were treated with an intravitreal injection of Conbercept at 5 d before surgery. The surgery for the three groups was observed, and the surgical time, intraoperative blood loss and incidence of iatrogenic hiatus were recorded. The subretinal neovascular membrane specimens of all patients were collected during the surgery to determine the expression levels of VEGF. The incidence of complications was observed, and changes in the best corrected visual acuity(BCVA) at different times before and after surgery were compared. Data were analyzed using a one-way ANOVA. Results: The surgical times and intraoperative blood loss of groups B and C were shorter and less than those in group A (P<0.05), and the rates of electric coagulation hemostasis during surgery, the incidence rates of the iatrogenic retinal hole and postoperative vitreous hemorrhage were lower than those in group A (P<0.05). The incidence rates of corneal edema, high intraocular pressure and anterior chamber inflammatory reactions in groups B and C after surgery were lower than those in group A (P<0.05), but there was no statistically significant difference between groups B and C (P>0.05). The positive rates of VEGF in the neovascular membranes of group B and group C were lower than that in group A, but the difference between groups B and C (P>0.05) was not significant. The BCVA of the three groups increased at 3 months and 6 months after surgery (P<0.05), and the BCVA of groups B and C at 3 and 6 months after surgery was higher than that of group A (P<0.05), without a statistically significant difference between groups B and C (P>0.05). Conclusions: Intravitreal injections of Conbercept on the 3 d and 5 d before surgery can shorten the surgical time, reduce the incidence of intraoperative and postoperative complications, reduce the expression level of VEGF in the neovascular membrane, and promote the recovery of visual acuity in patients with DR after surgery, without a significant difference between injections 3 d or 5 d before surgery.