Abstract: Objective To explore contamination risk while conducting human immunodeficiency virus(HIV) etiologic study in bio-safety level-III laboratory(BSL-3) in case of accidents,and to establish risk evaluation index for bio-safety management system in BSL-3 laboratory for HIV study.Methods Ink and pseudo-virus solution were used as samples to simulate laboratory accident to determine contamination extent.Swab samples taken from different contaminated spots were collected and tested for human immunodeficiency virus type 1(HIV-1) with quantitative real-time PCR.After disinfection procedures,swab samples from various spots were collected again and tested for HIV-1 to evaluate effectiveness of disinfection.Results While accidents occurred in bio-safety cabinet,the major contaminated sites were located in table surface of the cabinet where samples directly contacting with the surface in the radius of 15 cm,and its lateral walls and front as well.Glove surface was the most seriously contaminated.When different laboratory containers fell off to laboratory floor,major contamination was located in the places in front of the experimenter with a range of 60-degree of angle.The range of splash was positively correlated with sample size and its height.After on-site disinfection with 75% ethanol or/and 500 mg/L chlorine disinfectants,HIV-1 nucleic acid tests for samples taken from accident sites were all negative.Conclusion The study primarily determined the range and degree of contamination diffusion when laboratory accidents happened and common disinfectants can effectively kill HIV.