This paper calculates the static stress changes generated by the Yushu MS7.1 earthquake in Qinghai Province.On the basis of regional stress,we take into account the static stress change triggered by the Yushu MS7.1 earthquake to find the optional fault plane.We then calculate the coulomb stress changes on the optional fault.The results indicate that most of aftershocks are triggered by the main shock.The image of the coulomb stress changes is also in accord with regional earthquakes（ML≥3.0） distribution,but the value is lower than 0.01MPa.In addition,this paper calculates the coulomb stress changes of the aftershock fault planes same as the mainshock.The comparison with the results in the previous calculation shows that the image of coulomb stress changes obtained by using ＂optional fault＂ method is more consistent with the distribution of Yushu aftershocks and regional earthquakes.[著者文摘]