Aiming to improve the manufacturing accuracy of the build-in channels by selective laser melting (SLM), an anti-deformation model was established which was based on the simulation results of deformation and stress distribution of channel structure models with different length-depth ratios in SLM process by Simufact Additive software. It is demonstrated that the length of the channel structure is proportional to the deformation. Conversely, with the depth of the channel increases, the total distortion has a tendency of decreasing. The anti-deformation model can effectively reduce the amount of adhesive powder and deformation on the inner surface of printing parts, and improve the forming accuracy. In particular, the double-peak distortion occurs when the length and depth of the channel are 20 and 60 mm, respectively. Meanwhile, the roughness of overhanging surface is improved by 41.21% after compensating by anti-deformation mathematical model.