In this study, a geometry optimization of welding joint between tower and bottom flange in a wind turbine is performed based on residual stress considerations. A sequentially coupling finite element analysis (FEA) program is developed to simulate the welding temperature and residual stress. Using this FEA program, four FE models with different bevel are developed to calculate their residual stresses, which are compared to optimize the weld geometry. The results show that complex residual stresses are generated and concentrated in the fillet weld. Using K type bevel with internal concave fillet and outside convex fillet can obtain the minimal residual stress, which provides a reference the fabrication of wind turbines.