In view of the machining deformation of joint thinwalled parts, orthogonal designed experiment with three factors and five levels was established to optimize the milling cutter angels. The finite element analysis software ABAQUS was used to establish finite element model and carry on simulating processing. Through analyzing experimental results, the optimal combination γ=8°,α=5°,β=63°was obtained. The optimal milling cutter angel can make the average deformation less than that of the orthogonal experiments. By comparing with the actual experimental results, the validity of the finite element method is verified.The results show that optimum tool angel is an efficient method for controlling the machining deformation.