The nonlinear response of digital projector is a hot issue in recent years, because although the digital projector can avoid all kinds of defects of physical grating projection, its own nonlinearity directly affects the output information, which is the main source of phase error, and then affects the measurement accuracy. Aiming at the problem that Gamma nonlinearity in 3D measurement of digital fringe projection was inconsistent with Gamma value in different regions, a method of correcting Gamma nonlinearity by precoding of subregion of orthogonal fringes was proposed. By dividing the region by orthogonal fringes, the region fringe image was corrected by polynomial fitting and precoding value calculating. The phase error was reduced by 82.24% after correction by this method. It was suitable for the position relationship between any projector and camera. Only a set of precoding coefficients of subregion need to be calculated and encoded fringe graph can be generated by this method. The method can meet the measurement requirements of the system after that. The method has strong flexibility and high accuracy.