Abstract: In order to quantify the effect of the water curtain, the water curtain system parameters based on the water curtain momentum ratio R and the smoke resistance efficiency η are constructed through theoretical analysis. The FDS was used to simulate the 50 sets of working conditions under different water spray intensity and longitudinal wind speed for5MW,10MW and15MW fire scales. The results show that the larger the momentum ratio is, the lower the smoke resistance efficiency is. Under the three fire sources of 5MW,10MW and15MW, the best effective smoke resistance momentum ratio is 4.35×10³,2.44×10³,2.10×10³, respectively.The effectiveness of the water curtain to prevent smoke is verified from the microscopic (flow field). Under the three fire sources of 5MW,10MW and15MW, the optimal water spray intensity is 2.0L/(m·s)，2.0L/(m·s),2.5L/(m·s) respectively，and the water curtain spray intensity increases, the cooling effect increases, but the tunnel visibility decreases, and the smoke blocking effect is weakened.

Key words: underground road, water curtain system, momentum ratio, smoke resistance ratio, system parameters