Based on the stress-strain constitutive relationship of rock,we use the ground strain observation data that can reflect the change of rock strain as the"response amount",and apply the loading and unloading response ratio (LURR) calculation method include coulomb stress-triggered model to calculate the LURR results of the ground strain observation within 500km of the epicenter before the Jiuzhaigou M_S7.0 earthquake. Our results suggest that the method based on the strain observation is of better extracting the LURR anomaly from the tidal frequency band before the earthquake. We find that the LURR anomaly appeared in several strain observation stations within 300km before the Jiuzhaigou earthquake,and the maximum Y value of Liangshui station EW component at a distance of 96km reached 3.27. The spatial evolution characteristics of LURR indicate that the epicenter and surrounding areas have experienced an abnormal concentration-enhancement-weakening process within about 9 months before the earthquake. It is proved that under the background of long-term stress accumulation in this area,with the continuous accumulation of stress,the rocks are constantly damaged or weakened. Eventually,the accumulation of strain energy on the Shuzheng fault exceeds the strength of the medium and triggers this earthquake.