Abstract： Objective:To observe the effect of hyperbaric oxygen（HBO）in treating ulcerative colitis（UC）by systematic evaluation method.Methods:With “ulcerative colitis” and "hyperbaric oxygen" and related free words as search terms，the databases such as China National Knowledge Infrastructure（CNKI），Wanfang Data，Chongqing VIP，China Biology Medicine disc（CBM），PubMed，Embase，and Cochrane Library，were searched by computer to retrieve randomized controlled trials（RCT）on hyperbaric oxygen-assisted treatment of ulcerative colitis from the date of the inceptions of the databases to October 7，2021. The literatures were screened according to the proposed inclusion and exclusion criteria；the Cochrance Review Manual was used to assess the quality of the literatures；the heterogeneity test and meta-analysis of outcome indicators were performed with RevMan 5.3 software，and publication bias was tested with Stata 17.Results:A total of 10 RCTs and 664 patients were included. The results of meta-analysis showed that the treatments combined hyperbaric oxygen therapy could improve the effective rate of ulcerative colitis［ RR=1.30，95% CI（1.17，1.45）， P<0.001］and reduce the recurrence rate［ RR=0.30，95% CI（0.15，0.59）， P<0.01］. The funnel plot was roughly symmetrical，and the Begg’s test result（ P>0.05），suggested that there was no publication bias in the 10 RCT studies selected for this study. Conclusion:Hyperbaric oxygen as adjunctive therapy for ulcerative colitis can improve effective rate and reduce recurrence rate，which is superior to using conventional treatment alone.