Abstract: An efficient preconditioner is proposed to increase robustness and efficiency of iterative solutions of dielectric problems formulated with the combined tangential formulation(CTF)based on higher order hierarchical method of moments. It is found that the absolute values of coupled terms in discretized matrix equation highly contrast.Based on this fact,a reduced matrix equation is obtained by omitting the weak coupled term.Then a preconditioner is constructed from the reduced matrix equation by employing incomplete LU techniques.Numerical experiments confirm that the proposed preconditioner can significantly improve convergence rates and reduce the CPU time of dielectric problems formulated with CTF when maintaining the same accuracy.