This paper puts forward the triangle element method for calculating gravity anomaly of three-dimensional sphere-coronal model by using the divergence theorem. In this study, the volume integration was changed into surface integral, a series of triangles were used to fit the surface, and then the Green’s formula was adopted to change surface integral into line integral. At the same time, a reasonable calculation program was given. The surface gravity anomalies of homogeneous and non-homogeneous density sphere-coronal models were calculated and, as a result, the planar anomaly maps of the two models were drawn. An error analysis has proved the effectiveness and reliability of this method.