This paper aims to solve the problem that the thermal-mechanical coupled simulation almost impossible to predict the distortion of industrial-scale parts based on the modified inherent strain method. Firstly, the small-scale model is selected to simulate the laser melting deposition (LMD) process, and the inherent strain values are extracted from the thermal-mechanical coupled results. Secondly, the distortion of the substrate with clamped end is predicted by the inherent strain method after thin-wall parts deposited on it. By comparing with the thermal-mechanical coupled results, the deviation of the maximum distortion on the center line of the bottom surface is 3.27%, and the average distortion on the edge line is 4.15%. Meanwhile, it is found that 3 mm is the optimal height of equivalent numerical layer in the inherent strain method. Finally, the scanning path is optimized. On this basis, the distortion results of industrial-scale camshaft model fabricated by LMD process is calculated. The results show that the maximum distortion of the camshaft is 1.47 mm. After removing the support, both ends are warped upward, and the maximum distortion increases to 2.16 mm. The whole calculation process only takes 9.5 h, which is of great significance for the rapid distortion prediction of industrial-scale LMD parts.