Objective:To systematically evaluate the effect of different pressing time on bleeding in patients with subcutaneous injection of low molecular weight heparin (LMWH) .Methods:We retrieved the randomized controlled trial (RCT) or controlled clinicial trials (CCT) on local pressing time and bleeding in patients with subcutaneous injection of LMWH by searching PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI) , China Biology Medicine (CBM) , Wanfang Data and VIP from the database establishment to September 2019. Two researchers independently screened literature based on inclusion and exclusion criteria, evaluated quality and extracted data. RevMan 5.3 was used to conduct Meta-analysis on the extracted data.Results:A total of 9 studies that met the criteria were finally included and the included documents were all in Chinese, of which 4 were RCTs and 5 were CCTs. Subcutaneous hemorrhage diameter <5 mm was defined as no bleeding, subcutaneous hemorrhage ≥5 mm was defined as bleeding, and bleeding incidence was used as the final outcome indicator. According to different pressing time, they were divided into non-pressing group, group of pressing for 3 minutes, group of pressing for 5 minutes and group of pressing for 10 minutes, and were compared each group in pairs. Meta-analysis results showed there were significantly statistical differences between non-pressing group and group of pressing for 3 minutes [ OR=0.44, 95% CI (0.25, 0.78) , P=0.005], between group of pressing for 3 minutes and group of pressing for 5 minutes [ OR=2.12, 95% CI (1.18, 3.83) , P=0.010]; there were no significantly statistical differences between non-pressing group and group of pressing for 5 minutes [ OR=0.94, 95% CI (0.32, 2.81) , P=0.920], between non-pressing group and group of pressing for 10 minutes [ OR=1.11, 95% CI (0.33, 3.70) , P=0.870], between group of pressing for 5 minutes and group of pressing for 10 minutes [ OR=2.56, 95% CI (0.72, 9.11) , P=0.150]. Conclusions:Subcutaneous injection of LMWH without pressing is better than pressing for 3 minutes, and pressing for 5 minutes is better than pressing for 3 minutes. Considering the limited number of included documents and the quality grades are all B, research conclusions still need to be verified by large samples and rigorous experimental design.