The method of characteristic(MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System(PPFS) during the alternate startup process.The motion of check valve disc was simulated using inertial valve model.Transient parameters including the pressure oscillation,local flow velocity and slamming of the check valve disc etc.have been obtained.The results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps.The induced maximum pressure vibration amplitude is up to 5.0 MPa.The scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water hammer.It has been numerically approved to be an effective approach. The method of characteristic (MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System (PPFS) during the alternate startup process. The motion of check valve disc was simulated using inertial valve model. Transitional parameters including the pressure oscillation, local flow velocity and slamming of the check valve disc etc. have been obtained. The results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps.The induced maximum pressure vibration amplitude is up to 5.0 MPa. The scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water hammer. It has been numerically approved to be an effective approach.