Abstract: Lead-based reactor coolant has high thermal conductivity, good thermal expansion and strong natural circulation ability, which has outstanding advantages in safety, economy and miniaturization. At the same time, lead-bismuth reactors have potential applications in small nuclear power sources, marine reactors and so on. Difference from land-based nuclear power plants, marine nuclear power plants will produce swaying, heaving, tilting and other movements due to their long-term operation in the ocean environment. In order to study the thermal-hydraulic characteristics of the lead-bismuth reactor system under marine conditions, an experimental study was conducted by building a lead-bismuth experimental circuit based on a heaving motion platform. Under the influence of heaving motion, the flow rate of lead-bismuth circuit fluctuates and the flow resistance and heat transfer characteristics change. In this paper, the flow resistance and heat transfer characteristics of liquid lead-bismuth eutectic in a vertical circular tube under forced circulation under heaving conditions are investigated experimentally. The range of Reynolds number (Re) in the flow resistance experiment is 23 500-261 280, and the range of Peclet number (Pe) in the flow heat transfer experiment is 524.4 450. The results show that: The peak value of instantaneous additional pressure drop caused by heaving motion is lower than the theoretical value; The heaving motion causes periodic fluctuations in the flow rate of the circuit, and the maximum fluctuation is up to 16% in the low Re region; In the low Re region, the heaving condition makes the time-averaged frictional resistance coefficient of the pipe increase slightly; The relationship between the fluctuation of loop flow caused by undulating motion and the undulating acceleration and Re was obtained by fitting, which is in good agreement with the experimental results. This method can be used to predict the fluctuation of flow rate in the reactor at different coolant flow rates by heaving motion. In the scope of this experimental working condition, although the fluctuation causes the fluctuation of the flow rate, the instantaneous temperature difference between the inlet and outlet of the experimental section and the instantaneous heat transfer coefficient h of the experimental section do not fluctuate significantly, and the fluctuation has little impact on the instantaneous heat transfer characteristics. In the forced circulation, the heaving motion does not affect the heat transfer characteristics of the circuit. The results of this study can provide data reference for the engineering design of lead-bismuth reactor.