Abstract: The redundancy pump group is a common subsystem in nuclear reactor systems,because of its overlap of warm standby,common cause failure（CCF） and other dependencies,and special effect of check valve group working simultaneously,the high-order one has various states and complex operation.The paper applies the dynamic reliability block diagram（DRBD） to build DRBD model of redundancy pump group,clearly expresses dependencies or dependent behaviors,and dependency parameters between components,and applies Monte Carlo simulation to simulate its operation and plots its fault probability change graphs.The result shows that the combining of DRBD and MC simulation is an effective method to analyze the depend-ent-dynamic reliability of high-order redundancy systems.