Abstract: As one of the fourth-generation advanced nuclear energy systems, Lead-Bismuth Eutectic(LBE) cooled reactor has excellent neutron economy and inherent safety. To improve its compactness and safety, the main coolant system of LBE-cooled reactor tends to adopt the integrated pool structure design concept, but this design concept also introduces complex thermal hydraulic problems. To solve the above issues, the multi-physics coupling transient safety analysis code for LBE-cooled reactor MPC_LBE was developed, but this code uses a constant temperature simplified model which are not able to simulate the heat exchange process between the first and second circuits, and the accident transient simulation is rather conservative which deviating from the actual condition. To solve this problem, the numerical simulation method of the heat exchanger module for LBE-cooled reactor was carried out in this paper. A one-dimensional numerical calculation models were employed for the primary side, pipe wall and secondary side of heat exchanger, and the numerical heat transfer model was constructed. Finally, the heat exchanger module was coupled with the MPC_LBE code by external explicit means. For the heat exchanger numerical calculation module, steady-state verification and time step sensitivity analysis were performed separately, and the results show that the time step sensitivity of the explicit coupling strategy is large, while the time step setting of the implicit coupling strategy has almost no effect on the simulation results. For the new MPC_LBE program coupled with the numerical calculation module of the heat exchanger, the steady-state simulation application of the natural cycle lead-bismuth reactor was carried out.