Steam generator tube rupture (SGTR) is typical accident scenario in advanced lead–bismuth cooled fast reactor (LFR) and threatens the safety operation of reactor. During SGTR accident, water or water/steam mixture with high pressure in the secondary circuit is discharged through the break into the pool of molten lead–bismuth. At the rupture moment, a pressure wave forms and propagates in lead–bismuth due to dynamic interactions between the discharged water jet flow and liquid metal. Pressure wave may lead to the rupture of neighboring intact tube and further deterioration of the accident consequence. In this paper, to evaluation the mechanical load of pressure wave on heat transfer tube, a numerical method based on the Eulerian multiphase flow model is developed. Liquid metal, liquid water and steam are considered as compressible fluid. The continuity equation, momentum equation and energy conservation equation of each phase are solved respective. To verify the numerical method, the theoretical boiling liquid expanding vapor explosion (BLEVE) problem is modelled and the simulated time curves of pressure in liquid metal are compared with theoretical analysis results. On this basis, the molten lead–bismuth flow channel in broken steam generator of LFR is modelled and the first stage of SGTR transient is simulated. Pressure wave propagation at the downstream of break in lead–bismuth is caught in simulation. The result shows that the peak pressure reaches to >10 MPa within 0.1 ms after break occurs. Then the effects of break diameter and pressure of secondary circuit are analyzed. These studies provide the initial and boundary conditions for further structural response analysis on the neighboring intact heat transfer tube.