ObjectiveTo explore the retrograde contamination of drainage bag outlets, and provide basis for the formulation of related guideline for healthcareassociated infection(HAI) management. MethodsOn October 14, 2016, with sterile manipulation, urine, 5% glucose solution, glucose normal saline, sterile water, and 0.9% normal saline were injected into antireflux drainage bags (antireflux group) and common drainage bags (common group) respectively, entrances of bags were sealed and bags were hung in two ways: outlets were 10 cm away from the ground (suspended group) and touched the ground (groundtouching group) respectively, specimens were collected from bag outlets to perform bacterial culture every 3 days, a total of 10 times of cultures were performed, retrograde contamination of drainage bag outlets was observed dynamically. ResultsRetrograde contamination rate of drainage bag outlets of antireflux group was significantly lower than common group (7.7% vs 46.0%, P=0.000); suspended group was significantly lower than groundtouching group (17.9% vs 35.8%, P=0.000). Retrograde contamination rates of outlets of drainage bags filled with different properties of liquid were as follows: urine (54.3%)＞5% glucose solution (34.5%)＞glucose normal saline (24.3%)＞0.9% normal saline (10.8%)＞sterile water (10.5%), pairwise comparison showed a significant difference(P=0.000). The initial occurrence time of contamination in antireflux group and common group was on the 13th day and 7th day respectively, two group was significantly different on the 7th day(P=0.041). There was a medium intensity correlation between the types of drainage bags and liquid properties（Pearson C=0.5）. ConclusionDifferent types of drainage bags, retention time, and liquid property can impact retrograde contamination of drainage bag outlets, regular urine culture during the use of drainage bags should be paid attention in clinical practice, so as to use antimicrobial agents rationally and guide replacement time of drainage bags.