Abstract: To verify that the high-pressure cooler structure of the reactor coolant pump (reffered to as the main pump) can avoid the flow-induced vibration under normal operating conditions, this work analyzes the influence of the shell-side fluid on the vibration of the intermediate coil from three aspects, including the vortex shedding, the fluid-elastic instability and the turbulent excitation. The natural frequency of the helical tube equal to 1.877 Hz is determined by using the pre-stressed modal analysis for the comparison of subsequent evaluations. The vortex frequency is calculated for the maximum and the minimum flow areas, respectively, and the ratio of the natural frequency to the vortex frequency is less than 2. The flow velocity instability of the helical tube calculated by the Karman vortex frequency is higher than that of the shell side gap, indicating that the flow velocity of the inner shell side does not reach the critical velocity of the flow elastic instability of the helical tube. Besides, the center frequency of the turbulent excitation calculated by appropriate semi-empirical model of the helical tube bundle is 3.76 times the natural frequency of the helical tube. The results of these three calculations prove that the structural design of the HP-cooler is safe and reasonable, and can satisfy the requirements of nuclear power plants.