Objective To systematically evaluate the effect of needleless connectors on central venous catheterization(CVC)-related complications in patients. Methods Randomized controlled trials (RCT) on effect of needleless connectors on CVC-related complications in patients were retrieved from PubMed, The Cochrane Library, Web of Science, Embase, China Biomedical Literature Database, China National Knowledge Infrastructure(CNKI)and Wanfang Database, the retrieval time was from establishment of database to March 2018. Two researchers independently screened literatures according to inclusion and exclusion criteria, data were extracted, bias risk of included literatures were evaluated, Stata 12.0 software was used for statistical analysis. Results 29 RCTs,4 052 patients were included in the study, 27 literatures compared complications related to needleless collectors and heparin cap, and 2 literatures compared complications related to needleless connectors and tee connectors. Meta-analysis showed that the incidences of catheter-related blood stream infection (CRBSI)(RR, 0.25[95%CI, 0.18-0.35]), occlusion of catheter (RR, 0.17[95%CI, 0.13-0.23]), return blood (RR, 0.11[95%CI, 0.08-0.15]), phlebitis (RR, 0.21[95%CI, 0.11-0.41]), needle stick injury (RR, 0.12[95%CI, 0.03-0.43]), and extubation (RR, 0.100[95%CI, 0.038-0.259]) in patients with needleless CVC were all lower than those in heparin cap/tee connector group, difference were all statistically significant (all P<0.01). Conclusion Needleless connector can reduce the incidence CVC-related complications in patients.