Abstract: The Weisan Road Yangtze River tunnel of Nanjing is under high water pressure and passes through weak stratum. Fire may cause the failure of lining and the waterproof, resulting in tunnel leakage and water gushing, and it may cause destructive disasters of the tunnel. Based on the FEM analysis, segments under fire and different conditions are simulated, including construction stage, normal operation condition without protective measures and normal operation conditions with protective measures. The analysis shows that, at construction stage, the temperature near the waterproof is below 60 ℃, and the waterproof is in a safe state. Under operating conditions without fire prevention measures, after fire of 2 h, the maximum temperature near the internal waterproof is close to 300 ℃, and the waterproof will be burned. Under the protection of 30 mm-fireproof board, after fire of 2 h, the maximum temperature of the waterproof can be controlled below 100 ℃, ensuring the safety of the waterproof. The 20 mm-fireproof board can ensure the structural safety and the waterproof safety for 1 h under larger fire case, and 30 mm-fireproof board can ensure the safety for 2 h.