Data of artificial earthquake sounding, interpretation of gravity, geology, aeromagnetic detection, telluric electromagnetic sounding, seismic activity and geochemistry are used to study relationship between the 1920 Haiyuan M_S8. 6 earthquake and geologic structure. The result shows that the Haiyuan fault is an overlap fold-fault taking the shape of the shovel with depth less than 10 km, which bears no relation to occurrence of the 1920 Haiyuan earthquake because the focal depth of the earthquake is 15 ～ 20 km.The Haiyuan earthquake relates to both NS and EW structures extending to the top of the asthenosphere and the movement of the material of the asthenosphere. The ground deformation of all kinds along the Haiyuan fault are induced by the earthquake.