In this paper, according to the geological structure, geomorphic feacture and the characteristics of seismic activity, the author: divided the loess region of the Northwest China into four subregions and studied their attenuation laws of seismic ground motion. The results show that the attenuation rate of intensity as well as seismic ground motion becomes slower from the western region to the eastern region with the increasing of the thickness of soil stratum. Before statistical analysis, the authors made linear interpolation of isoseismic contours to consider the uncertainty of attenuation. The authors also put forward a new thought, that is, using the Q value to adjust the parameters of attenuation law of seismic ground motion.