Output of microwave have been increased with development of pulsed power system. The risk of RF front end system is dramatically increasing as the output of high power electromagnetic (HPEM) pulse increases. There are largely two ways of coupling HPEM pulse: (i) Front door coupling, which is through antennas and sensors to receive signals (ii) Back-door coupling, which is through unintended way such as punctures and slots. Compared to back-door coupling, front-door coupling is more risky and hazardous since it is coupled with intended parts. The simulation studies of this problem are conducted by numerical method. However it takes too many times in computation. In this paper, the in-line circuit modeling for damage analysis of the RF front end system affected by HPEM pulse is proposed. This integrated circuit modeling is simulated by the Electro Magnetic Transient Program (EMTP). It is simulated from the output of the HPEM system to the RF front end system. The target RF system of the study is the antenna. Passive circuit elements are used to model for antenna efficiency, propagation attenuation and etc.