Terrorist attacks and local wars occur frequently, which makes the risk of buildings subjected to multiple explosions increasing. Most of the existing research focuses on the single explosion scenario, and there are few studies on the damage effect of reinforced concrete structures under multiple explosions. In order to study the damage effect of reinforcement concrete beams under secondary explosion and offset the shortcomings of the existing research, relevant numerical analysis is carried out. The damage parameters of K&C concrete constitutive model are modified firstly. And the ALE method for FSI (fluid-structure interaction) is used to simulate the secondary explosion experiment of reinforced concrete beam with the full restart function of LS-DYNA. The numerical analysis results are well consistent with the test results, verifying the effectiveness of the simulation method and the modified constitutive model. On this basis, the secondary explosion simulation conditions are expanded. The effects of various parameters, including scaled distance, concrete strength, longitudinal reinforcement ratio and transverse reinforcement details, on the damage effect of typical size reinforcement concrete beams under secondary explosion are further analyzed. The results show that due to the compressive membrane action of reinforcement concrete beam, keeping the total equivalent TNT weight of the explosion unchanged, the damage of RC component caused by one single explosion is more serious than the cumulative damage caused by two successive explosions. The concrete strength has a more significant effect on the blast resistance performance of RC beams under secondary explosion, the higher the concrete strength, the smaller the damage degree of the beam under the secondary explosion. Increasing the longitudinal reinforcement ratio has no obvious effect on improving the blast resistance performance of the beam and educing the transverse reinforcement spacing can effectively reduce the shear failure degree of reinforcement concrete beam which makes the blast resistance performance of RC beams under secondary explosion and near explosion improved. The iso-damage curves of reinforcement concrete beams with two different design parameters are further calculated and the corresponding damage degree zoning maps are established. The present results can provide reference for the blast resistance design of reinforcement concrete structures.