The deformation band of Tuosuohu earthquake Jan. 7, 1937(M=7.5) was 300km long. Strike as a whole was N70°W, in keeping with Kusaihu and Maqu fracture zone. This deformation band consists of a series of fault scarps, little upheavals, tension fissures, fault ridges and small segs. The combination of all deformation phenomena has shown that earthquake fracture is compressional with anticlockwise torsion characteristics and that the direction of compressional stress of earthquake region stress field is NEE-SWW. The structure of upheavals and segs of NNW direction, has intersected with the fracture Kuma in the earthquake region. The said structure has impeded the anticlockwise torsion of the fracture Kuma. Stresses have been congregated here. That was the essential cause which led to the occurrence of this strong earthquake.