In this paper, a static electromagnetic field problem will be solved. The method to solve the problem is Finite Difference Method ( FDM ). The software MATLAB is the main environment used to finish the numerical computing. Finally, we found using Finite Difference Method to solve a static electromagnetic field problem is quite convenient. We also can draw the two-dimension and three-dimension graph of the distribution of the electromagnetic field. Furthermore, we discuss the advantages of using FDM to solve the problem, and the disadvantages still exist in this method.