After the 2014 Yutian MS7. 3 earthquake，as the impact of the relation with tectonic and seismic activity，the earthquake risk in the North South Seismic Belt is a matter of concern． Using the catalog provided by China Earthquake Networks Center，the Benioff strain ratio is calculated in the North South Seismic Belt 30 days before and after the March 21，2008 and February 12，2014 Yutian MS7. 3 earthquakes． The results show that the main shocks with M ＞ 5. 0 within one year all occurred in the area near the high strain ratio or the junction area of the high and low strain ratio after the 2008 Yutian MS 7. 3 earthquake． The activity of strong earthquake coincides with the high strain ratio obviously． This reflects the high stress level in the regions． The area with high stress easily releases some small earthquakes after the Yutian earthquake and the research has certain significance for the strong earthquake．