Purpose: To introduce the application of intraoperative optical coherence tomography (iOCT) in pars plana vitrectomy (PPV) for various vitreoretinal diseases, and to report the 4-year assessment of feasibility and utility in Chinese population. Methods: Retrospective case series of patients who underwent PPV and iOCT scan at Eye Hospital of Wenzhou Medical College from January 2016 to January 2020. Clinical characteristics were documented before operation, and we intraoperatively recorded the time and results of iOCT scanning, specific surgical maneuvers performed, the consistency with the planned strategies before surgery, the type of OCT images obtained, and adverse events (AEs). The surgeon feedback was collected to evaluate the utility of iOCT during surgery. Results: In total 339 eyes successfully completed iOCT scan, with an average scanning time of 3.54 ± 2.3 min, including 59 cases of idiopathic macular hole (iMH), 134 cases of idiopathic epiretinal membrane (iERM), 33 cases of lamellar macular hole (LMH), 40 cases of high myopic maculopathy, 13 cases of vitreous macular traction (VMT), 60 cases of dense vitreous hemorrhage (VH). The iOCT findings were not consistent with examination under the operating microscope in 49 cases (14.5%), including 29 cases (8.6%) which changed the operation strategies during surgery. The Hole-door phenomenon arose in 20 cases (33.9%) of iMH and 3 cases (25%) of high myopic MH after ILMs peeling. Moreover, the residue ERM was observed in nine cases (6.7%) of iERM and two cases (14.3%) in high myopic ERM after ILMs peeling. Some new surgical methods could also be confirmed using iOCT. Conclusion: The application of iOCT has a significant clinical functionality in vitreoretinal surgery, providing the surgeon with a new surgical understanding, guiding the selection of a more reasonable operative procedure during surgery, predicting postoperative recovery and improving postoperative outcomes.