Abstract: In order to research the influence of covering thickness on explosive welding, the explosive welding experiments under different covering thickness are simulated in three dimensions by using ANSYS/LS-DYNA software and combining the SPH-FEM coupling algorithm. The Q235 steel with the thickness of 20 mm and the 304 stainless steel with the thickness of 2.5 mm are used as the base plate and the flyer plate in the present study. The dynamic parameters in the welding process are calculated according to the corresponding material parameter theory, and an explosive welding window is established. The simulation results show that, compared to the explosive welding without covering, the impact velocity is increased by 39.3%, 58.1% and 68.8% respectively when the covering thickness is 15 mm, 30 mm and 45 mm. And the collision pressure is increased by 41.0%, 65.6% and 80.6% respectively. The simulation results approximately agree with the experimental results. The SPH method is used to carry out two-dimensional numerical simulation to obtain the composite interface between flyer plate and base plate when assembling covering. The simulation results show that the composite plate has a good waveform composite interface when the covering thickness is 15 mm, and the interface waveform is more consistent with the results of the metallographic analysis in the experiment.