Abstract: The theory of the point-mass model is one of the most important methods for the research of the logical gravity field. In this paper, the approximation theory of point-mass model is briefly introduced, and the characteristics of the elements in the coefficient matrix for the model construction are analyzed by numerical calculation. The observations are calculated by using EGM2008 with degree and order 720 in the region of 32~34N and 103~105E. The four-tier point-mass groups based on the geopotential model with degree and order 36 are from low frequency to high frequency to approximate the gravity field. The results of the tests show that the effect of three-tier point-mass model is better than others and the truncation error of gravity disturbance created by using the point-mass model is less than 2 mGal on the radial direction.