Based on the Lanzhou seismic network observational report, using the multi-station methods, the seismic velocity ratio （Vp/Vs） of the 2 953 earthquakes in Northeastern margin of Qinghai-Tibet block during Jan. 2001 to Jun. 2007 are calculated. The research region are divided into little areas by 1°× 1° and 0.2°×0.2°, and the average seismic velocity ratios for every little areas are given. Through analysising the average seismic velocity ratios, following conclusion are gottern： （1） The average ratios in different regions of the research block are different, among them, the ratio in Southeastern of Gansu province is the highest, in Qilian seismic belt and along West Qinling fault are higher also, in middle Gansu province is the lowest. （2）The mine earthquakes often occurred in the 1°× 1° little areas with lower ratios, so the ratio could be used to distinguish mine earthquake. （3） The ratio values increase along with the increase of magnitudes of earthquake. The average seismic velocity ratios for each area in Northeastern margin of Qinghai-Tibet block can be a reference to analyze the variation of the ratio before strong earthquakes.