The promotion of hydrogen fuel cell vehicles (HFCVs) has been hindered by hydrogen safety issues. In this paper, hydrogen leakage in an underground garage with smoke barriers is numerically simulated. Nine vents are arranged for the distribution of smoke barriers, and the effects of the ventilation mode and ventilation opening time on hydrogen dispersion and hydrogen removal efficiency are discussed. It is found that ventilation can effectively inhibit the formation of flammable hydrogen clouds. The hydrogen removal efficiency of mechanical ventilation is much higher than that of natural ventilation, and the effect becomes more significant as the ventilation time increases. Reducing the opening time of ventilation can improve the overall ventilation effect and the efficiency of removing high concentration hydrogen, while reducing the time required for hydrogen concentrations to drop below the safety limit.