It is found that an uniform stress field is exists in west of China by analysising the data of borehole strain from Wudu,Gaotai stations in Gansu province and Panzhihua, Xichang stations in Sichuan province, and the stress field is consistent to the mechanical charactor of deformation belt of west to Kunlun Mountain Pass M_S 8.1 earthquake on Nov. 14, 2001. All the strain data in 4 stations show the obvious short-term anomaly before the 8.1 earthquake.