Based on the seismic observation report data provided by Xinjiang Digital Seismic Network from 2009 to 2014，we calculated the wave velocity ratio and its background value for medium and small earthquakes by using the multi-station method in the Tianshan region，Xinjiang. This paper analyses the variation of wave velocity ratio disturbance value to highlight the anomaly and also trace back seven moderate earthquakes at research area. The results show that: (1)the background value of the wave velocity ratio is almost 1.70. The wave velocity ratio obviously decreased in middle-eastern part of Tianshan Mountains and the region near Puchang Fault; (2)the wave velocity ratio disturbance value is lower at the epicenter before 4 earthquakes with M≥5.0 from 2011 to 2013 of the study area; (3)before 7 moderately strong earthquakes，the earthquake events with low value of wave velocity ratio account for over 60% of corresponding total events near the epicenter. The low value of wave velocity ratio is relatively obvious before moderate earthquakes.