Abstract: On basis of digital seismic observation data in Shanxi province,using single earthquake multistation Wadati method and multi-earthquake and multi-station joint method,this paper calculated the velocity ratio of seismic waves (V_P/V_S)in northern,central and southern Shanxi area.Analytical investigation shows that:before Hejin-wanrong 4.8 earthquake on January 24,2010,the Datong 4.5 earthquake on June 5,and Yangqu 4.6 earthquake,there is wave velocity ratio drop phenomenon.The top 2 earthquakes occurred in the process of wave velocity ratio decline,and the third earthquake occurred in the recovery phase.Then,wave velocity ratio in central and northern Shanxi keeps in low condition,especially the northern Shanxi area,which indicates that the northern Shanxi area is in risk of earthquake.