Abstract: The 73-node model of containment subcompartments for AP1000 nuclear power plant was set up using TMD code. Then 3 kinds of breaks with representative sizes and types were selected in order to calculate the pressure response of subcompartments due to breaks at different locations. Besides, the influence of model and input parameters was evaluated to get the results of limiting cases, and the weak nodes of containment subcompatments were identified. The results show that the maximum differential pressure can be reduced so as to increase the safety margin by enlarging the flow area of weak nodes.