On the bases of the regional seismic tectonics, deep geophysical characters and the basin structure of Lanzhou area, the 3D seismotectonic model is created for earthquake occurring on west part of north Mahanshan fault, and the earthquake deformation influence to Lanzhou basin is calculated on the case of earthquake Ms = 7. The results show that the deformation in Lanzhou basin has certain degree of attenuation and the total displacement of ground surface is from 1.25 m to 0. 3 m from west to east of the basin. The maximum earthquake stress is about 0. 02 MPa in the basin and only reached to 0.2 MPa on parts of the basin edge and front of high terraces. Although the earthquake strain has differentiation in east basin and west basin, the main strain magnitude is 10^-5 and only a few abnormal points reacbs to 10^-4. The deformation would not cause destruction such as ground fracture, and the effect to buildings＇ permanent deformation is weak also. But we should pay attention to the local abnormal effect near the boundaries of geomorphic elements and faults as well as the secondary hazard may be triggered.