To investigate the effectiveness of two regimens of ranibizumab-assisted pars plana vitrectomy (PPV) in the treatment of patients with proliferative diabetic retinopathy (PDR).This is a prospective, 6-month, randomized, controlled trial. 80 patients with 87 eyes requiring PPV treatment for PDR were included and randomly divided into a 1.0-mg injection group and a 0.5-mg injection group. The ranibizumab was delivered intra-operatively, at the close of surgery. The vitreous hemorrhage (VH) grade, best corrected visual acuity (BCVA), central macular thickness (CMT) and safety data were assessed to Month 6.The 1.0-mg injection group had a milder grade and a lower reoccurrence rate of early postoperatively VH than the 0.5-mg injection group (35.0% and 63.4%, respectively, P =0.0195). The mean BCVA of two groups was significantly improved from baseline to 6 months after surgery,1.60 ± 0.72 LogMAR (<20/200) to 0.47 ± 0.49 LogMAR (20/59) for the 1.0-mg injection group, and 1.51 ± 0.69 LogMAR (<20/200) to 0.50 ± 0.31 LogMAR (20/63) for the 0.5-mg injection group, but there was no significant difference between the two groups (P = 0.74). There was no significant difference in the mean decrease in CMT and probability of postoperative adverse events between the two groups.Intravitreal injection of 1.0 mg of ranibizumab after PPV compared with the recommended dose of 0.5 mg significantly reduced the recurrence and severity of early postoperative VH in patients with PDR. It also contributed to the early recovery of visual acuity after surgery and did not increase postoperative adverse events.Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Opthalmic Communications Society, Inc.