In phase measuring profilometry, the system gamma nonlinearity makes the captured fringe patterns non-sinusoidal, which causes the computed phase to exist a non-ignorable error and seriously affects the 3D reconstruction accuracy. Based on the detailed study of the existing gamma nonlinearity compensation and phase error reduction technique, a method based on low-pass frequency domain filtering is proposed. It mainly filters out higher than one-order harmonic components induced by the gamma nonlinearity in conditions of holding as much power as possible in the power spectrum, thus improves sinusoidal waveform of the fringe images. Compared to other compensation methods, the complex mathematic model is not needed in the proposed method. The simulation and experiments confirm that the higher-order harmonic components are significantly reduced, the phase precision can be effectively improved and a certain accuracy requirement can be reached.