Abstract: Jet flow gallery ventilation is a common method of construction ventilation. In order to investigate the flow field and the distribution of pollutants of gallery ventilation, it established a three-dimensional numerical model with fluid dynamic software Fluent based on Huayingshan tunnel project, studied the ventilation flow field and the distribution of hazardous gases in condition of sulfureted hydrogen gushing when tunnel passes through mined-out area. The results show that air distribution of current ventilation mode is unreasonable and results in a low air velocity zone with high concentration of hazardous gases. This problem can be solved by increasing air supply volume at tunnel face and installing local ventilation fans. When air velocity reaches 26 m/s in air duct the low air velocity zone disappears completely. With local ventilation fans in front of the cross passage, the air velocity in tunnel can reach 2 m/s and the low air velocity zone can also be eliminated.