The aircraft’s landing is guided by the instrument landing system (ILS). However, the guidance information may be disturbed by reflections from irregular terrain and obstacles. A sketch which restrains the multipath effect from irregular terrain and obstacles, is then required. This paper proposes a metallic reflective structure which aims at blocking the radio wave directly radiating to the terrain. The design of the structure size and location is based on the location of the obstacles and the radiation pattern of the antenna. Due to the fact that the scattering effect of the structure should be accurately simulated, the finite difference time domain - parabolic equation method (FDTD-PE) is applied in ILS and used to simulate the interaction of the scattering effect between the structure and the terrain. The experimental results show that the proposed method improves the multipath effect mitigation.