The investigation for the change of structure stressfield of the crust is one of the important approaches to earthquake prediction. The data analysis on the enlarged tests of a stress-strain observation system of resistance type has shown that in western Sichuan the change in this structure stress field always takes place with time and space.
The repeated alteration of the following factors are the immediate reason why the strong earthquakes prepare and occur one by one in this area. They are: accumulation intensifcation, relase and reversion. Luding seismic station had found that before Daofu earthquake of M=6.9 on January 24th, 1981, the direction of the compressive principal stress in the structure stress field had a deflection, near to 90° which lasted 36 days. Stress direction returned to normal 9 days before the earthquake. It has been observed that in western Sichuan, the structure stress field has been in a relatively steady state since Ganzi earthquake of M=6.0 on June 16th, 1982 but in the south it is in an increasing activity, As a result, this new kind of property leads the west of Sichuan to a calm part. but as for the western and northeastern parts of Yannan and fracture zones in Yuanjiang and Honghe are more active and were once hit by strong and moderate earthquakes from 1982 to 1983.