The authors used digital wave data of earthquakes in the middle of Tianshan mountains，Xinjiang and Heda method of multi-stations to calculate changes of wave velocities ratio before and after the Hejing M5. 6 earthquake on August 30，2008． They obtained the result as follows: ①In space，it forms a low value area of ellipse before the Hejing earthquake with M5. 6． The half of the long axis is approximately 70km，while that of the short axis is approximately 65km． And the trend of the ellipse is NE． The Hejing M5. 6 earthquake occurred in northwest part of the ellipse． ②Temporarily，it appeared as low value abnormity of 10 months before the Hejing M5. 6 earthquake． Before this earthquake，the value was obviously high． It forms a model of normal-fall-high value-earthquake． In the calculation process，the error of wave velocities ratio is controlled in less than 0. 05， and the correlation coefficient reached above 99. 0%．