Aiming at the problem that the Gamma nonlinear effect of the projector and the camera will cause periodic errors in the unwrapping phase results, a phase error suppression method based on the mean template is proposed. First, Fourier transform is performed on the unwrapping phase to calculate the period value of the phase error. Then, a one-dimensional mean filter template with variable length is designed. The length of the template is related to the period of the phase error. Finally, this template is used to perform mean filtering on the unwrapping phase to eliminate periodic errors. Experimental results show that the proposed method reduces the periodic error of the unwrapping phase by an average of 94%, eliminates the distortion ripples that appear when measuring the depth information of flat objects with structured light, and improves the accuracy of phase measurement and depth information measurement without complex mathematical models and increasing fringe patterns. The proposed method is more suitable for practical applications.