The stress field in larger area (from 34°N, 100°E to 41°N，106°E) of Qilianshan area have been studied using the data of mechanisms of moderate-strong earthquakes in the area from the GCMT catalogs of Columbia University; The focal mechanism solutions and the seismogenic stress field have been inverted for the small-moderate events based on the data from the networks set by China and France and the Gansu digital monitoring network using the joint inversion method of first motion and amplitude ratio of P and S wave. The results shoe that the tectonic stress of this area is a horizontal compressive stress with north-east direction of 40°~45°. The direction of main pressure stress in the area of Jingtai is about north-east with 45°, the type of most earthquakes are strike. There are quite a part earthquakes of reverse fault distributed in Tianzhu-Gulang area with horizontal stress of  main compressive with about 60°and advantage elevation angle about 10°. It is accordance with the tectonic stress and fault distribution in larger area.