The explosion of conventional ammunition near a nuclear power plant may cause damage to the main structure of the nuclear power plant. In order to evaluate the anti-explosion performance of the containment barrel wall, according to the resistance design curve of the structure, a new method for judging the explosion resistance of the simple support wall is proposed, and taking the reinforced concrete wall in the nuclear power plant as an example, the maximum incident pressure and explosion safety distance that the simple support wall can withstand are given, when the ductility coefficient is 3, the wall thickness and reinforcement ratio are the same, the design resistance is doubled, and the minimum safe explosion distance of the simple support wall is reduced by 12%; The resistance and reinforcement ratio are the same, and the minimum safe explosion distance of 600 mm thick is reduced by 450% compared with 3 mm thick simple support wall.The calculation results show that the design resistance, wall thickness and reinforcement ratio have different effects on the maximum overpressure value that the simple support wall can withstand and the minimum safe explosion distance without damage. This method and calculation results can be used to make a preliminary judgment on whether the safety of nuclear power plants can be guaranteed after an attack.