Electromagnetism characteristics of large complex target are analysed by combining multilevel fast multipole method and ILUT preconditioner. We must solve a linear system when solving electromagnetic integral equation by moment method. Multilevel fast multipole method is used to fast calculate the matrix-vector product when we solve the linear system by iterative method. ILUT preconditioner is used to reduce the prove condition number on the linear system and speed up the convergence iterative method. Numerical experiments show the robustness of our method.