Abstract: The magnetic field distribution during resistance spot welding(RSW) will affect the magnetic force acting on nugget and therefore, influence the nugget formation. At the same time, the magnetic field distribution also affects the electromagnetic environment, which influences the assessment of electromagnetic field exposure safety. This paper builds a finite element model of RSW according to the circuit of spot welding power source. The magnetic field during RSW of ferromagnetic workpieces was calculated, and experiments were carried out to verify the simulation. The results show that the maximum magnetic induction density was up to 7 T in the ferromagnetic workpiece. This indicates that the magnetization of ferromagnetic workpieces plays an important role in the nugget formation as well as its growth and it should not be ignored. The measured and calculated magnetic induction density agrees well, which verified the reliability of the finite element model.