Abstract: The double gear pump is the equipment of the steam turbine feed pump, which is one of the important equipment in the secondary circuit of the reactor. Its smooth operation can ensure a stable water supply source for the steam generator. In this paper, the duplex pump is briefly introduced, and in view of the problem that this type of duplex gear pump can not maintain the safe oil pressure in the normal range during the operation and debugging, the duplex pump is disassembled, the causes of the failure of the duplex pump are analyzed and found out, and the design of the duplex gear pump is optimized. After the performance verification test, the improved duplex pump solves this problem and ensures the normal operation of the steam turbine feed pump.