Abstract: In present study, the effects of the resistance-assisted heating process on the formability of 2519-T87 friction stir welded joints were investigated by experiments and numerical simulations. Based on the coupled Eulerian-Lagrangian (CEL) method, a three-dimensional thermal mechanical coupling model of friction stir welding with a resistance-assisted heating process was established. The temperature field and material flow behavior were analyzed, and the mechanism of eliminating tunnel hole defects during resistance-assisted heating friction stir welding process was discussed. The results show that the auxiliary heating process increases the welding peak temperature from 483 ℃ to 549 ℃, increases the residence time at high temperature above 350 ℃, and expands the high-temperature distribution area. This reduces the material deformation resistance, and enhances the fluidity of materials from the retreating side of the nugget zone to the advancing side, leading to more sufficient backfilling of materials, thus eliminating the tunnel hole defects in the joint.