Hydrogen fuel cell vehicle is an important development direction for hydrogen energy applications. In order to explore the impact of leakage speed and ventilation speed on hydrogen diffusion of fuel vehicles in garages, on the basis of the FLACS software of computational fluid dynamics, a multi-obstacle garage model with regular parking of vehicles was established. The leakage point was set at the bottom of vehicle, and the exhaust fan was set at the center of garage. The hydrogen leakage of fuel vehicles in the garage was simulated. The results show that the hydrogen diffusion in the garage is divided into three stages: collision diffusion, floating, and top layering. The hydrogen diffusion behavior is related to leakage speed, ventilation speed; as leakage speed increases, the hydrogen concentration on the ground near wall becomes larger, the hydrogen concentration at the height of human body becomes smaller; ventilation speed has a greater impact on the hydrogen concentration distribution in the two stages of ascending and concentrating stratification. In the ascending stage, the hydrogen concentration in the headspace of vehicle increases with the increase of ventilation speed; And in the stage of gathering the top layer, when ventilation speed increases, the hydrogen gathering effect in the upper corner of wall becomes more obvious.