Abstract: Owing to the limited space in the marine nuclear power plants, the lifting height for the condensate system is quite short, which can induce the cavitation of the condensate pump. To solve this problem, a jet pump is mounted in front of the condensate pump. Nevertheless, the cavitation risk also exists on the jet pump in the harsh ocean environment such as rolling motion. Therefore, the cavitation characteristics of the jet pump are investigated by CFD numerical method under the stable condition as well as two rolling motion condition. The results show that under the stable condition, the void fraction inside the jet pump flow field is very small, and the nozzle exit and throat pipe forepart are two positions prone to cavitation. Ocean rolling motion results in the enhancement of the cavitation of the jet pump and the decreasing of the lift range. The more frequent the rolling, the greater the effect. Especially, when the rolling motion period is 3 s, the cavitation of the jet pump develops seriously, the pump lift surges and is less than the rated lift evidently, which affect the operation safety of the condensate system.