Reinforced concrete (RC) shield building as the first external defense layer of AP1000 structure plays an important role in protection the population and environment when against the outer explosion. The strain rate effect of reinforced concrete was taken into consideration in the establishment of an AP1000 nuclear island structure-air-explosives fully coupled model by using the software AUTODYN. Object using damage mass as index, to infer the degree of damage. This paper studied the pressure evolution and damage mechanism. The analysis results provide valuable data on improving the anti-explosion capabilities in design based on the damage characteristics.