Abstract: A Ms 7.3 scale earthquake occurred in Yutian area, Xinjiang Uygur Autonomous Region, China, on March 21, 2008 is the biggest earthquake after the Ms 8.1 scale earthquake happened in Kunlun Mountain, November, 2001.Earthquake is concentrated reflection of tectonic activity, it can be accompanied by a large surface deformation and apparent fracture events, it can zoom the normal activities way of construct.Coseismic deformation is the effect directly reflected in the surface, it is very important for understanding of the nature of earthquake faulting and researching adjacent tectonic activity.In the harsh natural environment of northwestern margin of the Tibetan Plateau, the conventional methods can not carry out timely and effective for the field earthquake coseismic deformation measurement, so the advantages of InSAR technique have be highlighted.This article describes the InSAR observation principle, then gotten Yutian earthquake Co-seismic InSAR deformation field by ALOS PALSAR radar data, and presents geological results: Yutian Ms 7.3 earthquake macroscopic epicenter is located in the two north-south branches of Kangxiwar Fault southeast(Large Tamarisk Fault and Mousse Hill Fault) and the three branches of the triangle intersection which in Altyn Tagh Fault southwest; Yutian earthquake triggered a coseismic surface rupture which in Altyn Tagh Fault NS-trending branch, and the length of the rupture is 25.6 km; It is speculation that Yutian fault focal mechanism solutions is the normal fault under the deformed image of the interference radar, faults incline to west, the maximum range of motion on the plate over 200 cm; The tectonic stress around the two big faults intersection where Yutian earthquake occurred is mainly press in north and south direction.