The finite element simulation software SYSWELD is used to numerically simulate the temperature field, residual stress field, and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles. The simulation results show that as the welding heat input increases, the peak temperature during the welding process is higher, and the residual stress increases, they are all between 330–340 MPa, and the residual stress is concentrated in the area near the weld. The hole-drilling meth-od is used to measure the actual welding residual stress, and the measured data is in good agreement with the simulated value. The type of post-welding deformation is angular deformation, and as the welding heat input increases, the maximum deformation also increases. It shows smaller residual stress and deformation when the groove angle is 40° under the same heat input. In engineering applications, under the premise of guaranteeing welding quality, smaller heat input and 40° groove angle should be used.