The convolution effect in phase measuring profilometry, which is caused by the point spread function in optical imaging devices, is investigated, and a method for estimating the convolution parameters of the point spread function is proposed. This method can be used to assess the point spread function parameters by utilizing the influence of convolution effect on the intensity modulation parameters in phase measuring profilometry, wherein the modulation ratio of the base frequency to the other higher spatial frequency is calculated. By adopting the resulting estimated parameter, a convolution model is established for phase correction in error areas; thus, the 3D reconstruction accuracy is improved. The simulation and experimental results both verify the efficiency of the method. Compared with that obtained before correction, the root-mean-square error of phase is decreased by 30.55%.