Abstract: In order to explore the effect of ocean rolling conditions on thermal stratification and fluid solid heat transfer in the pressurizer surge line of nuclear power plant, the thermal stratification phenomenon in the pressurizer surge line with three-dimensional full-scale modeling was numerically simulated by using computational fluid dynamics software FLUENT, and the flow and heat transfer phenomenon in the surge line with rolling motion was compared and analyzed. Different from the previous method of adding rolling motion, the simulation of motion process could be realized by using the calculation model of FLUENT. The calculation results show that obvious thermal stratification appears in the surge line under the outsurge transient condition. The addition of ocean conditions can obviously improve the thermal stratification in the surge line, but it may bring about thermal oscillation. The results of the flow and heat transfer in the surge line are related to the velocity, the period, the amplitude and the axis of the rolling motion, which provides some ideas and results for the follow-up study of the thermal hydraulics under the rolling condition.