Abstract: In this paper, a finite element model of fiber laser welding-brazing process for steel/Al dissimilar metals was established by ANSYS. The accuracy of the finite element model was verified by fusion zone boundary criteria. The stress field and welding deformation were simulated based on this mode. The results showed that the peak tensile stress along welding direction appeared on the lower surface of the steel and near the welds behind the heat source. This peak tensile stress increased continually with the welding process continued and it reached a maximum of 203 MPa when welding finished (13s). The stress distribution was asymmetric and there was high stress gradient close to the heat source. The maximum deformation of the specimen was 0.882 mm.