Abstract: To study the effect of evaporation and humidification characteristics of spray water curtain on the relative humidity of the tunnel, the calculation model for relative humidity was established in the spray space. The effect of different control parameters on the humidity in the tunnel was explored based on numerical simulation. The results show that the mathematical model of spray droplet evaporation and humidification can effectively predict the relative humidity of roadway; the spray flow rate and atomization pressure, the air supply volume of the air duct, the ambient temperature, and humidity all contributed significantly to the relative humidity of the tunnel. By optimizing the parameters, it is possible to not only reduce the effective range of spray humidification on tunnel humidity but to also improve the moisture removal efficiency after spraying.