Abstract: OBJECTIVE To detect the non-tuberculous Mycobacterium（NTM） in the water of dental unit water line system（DUWLs） in 29 medical institutions of Shanghai and investigate the current situation of disinfection of related equipment waterways.METHODS The water samples were collected from the dental unit waterlines and incubated on 7 H10 agar plates after membrane filtration. All suspected isolates were examined by acid-fast staining and then identified to species by matrix assisted laser desorption/ionization time-of-flight mass spectrometry. At the same time, the questionnaire survey was also conducted to collect relevant data.RESULTS A total of 204 water samples were collected, including 40 ultrasonic water samples, 53 dental hand-piece water samples, 55 three use nozzle water samples and 56 gargle water samples. The total detection rate of NTM was 15.19%（31/204）, Mycobacterium mucogenicum（17 strains, 50.00%） and Mycobacterium cheloni（13 strains, 38.24%） were dominant. There was significant difference in the detection rate of NTM among the different sites（P＜0.05）. The detection rate of NTM was the highest（25.45%） in the three use gun water samples, and the detection rate was the lowest（2.50%） in the ultrasonic water samples. There were no significant differences in service life period of pipeline and detection rate of NTM.As compared with the frequency of disinfection, the detection rate of NTM was the lowest in the water pipelines with the time interval of disinfection less than 3 month（P＜0.05）.CONCLUSION The detection rate of NTM is 15.19% in the DUWLs of 29 medical institutions in Shanghai. The frequency of disinfection is a major influencing factor. It is necessary to strengthen the monitoring of the source water and take effective measures for disinfection.