Abstract: Surface integral equation (SIE) method combined with mode matching (MM) method is used to simulate the radiation problem of aperture antenna with dielectric structure. The mode matching method is used to describe the excitation model of the horn antenna. The metal wall of an aperture antenna is treated as a perfect electric conductor (PEC). The Electric Field Integral Equation (EFIE) is established on PEC. Both of the EFIE and the Magnetic Field Integral Equation (MFIE) are established on the surface which encloses the dielectric structure to form the PMCHW formulation. The combined formulations are solved by using the method of moment (MOM). Two typical numerical examples are given in this article. It shows that the results given by EFIE-PMCHW-MM hybrid method match well with the results given by commercial code FEKO. Furthermore, EFIE-PMCHW-MM hybrid method increases the calculation efficiency and decreases the computer resource consumption than VSIE-MM method.