The image method is a basic method to solve electrostatic field. This paper has used capacitance and charge methods to obtain multiple image charges of a system of three metal spheres. The distribution of electrostatic field is calculated by the effective and image charges. The numerical results confirm the consistence of the derived analytic results. The transition from attractive to repulsive interaction between two metal spheres can be realized by modulating the position and charged quantity of third metal sphere. By using Matlab software，the distribution of electric potential is directly compared for the system of two and three metal spheres.