Abstract: On 10th November 2008,a Mw 6.3 earthquake occurred in the Dachaidan region,Qinghai province,whose seismogenic fault is situated in Dachaidan-Zongwulongshan fault zone which is located on the northeastern margin of Qinghai-Tibet Plateau.A coseismic deformation field of the earthquake is constructed from ESA Envisat/ASAR radar images using 2-pass differential interferometry.The root mean square error of the InSAR coseismic deformation field is 0.52 cm with a spatial decay distance of 5.9 km,which are estimated using 1D variance-covariance function.The fault geometry is inverted using a rectangle dislocation model in the elastic half-space and the optimal coseismic fault slip model is determined based on the automated fault discretization method using the observed InSAR data.The inverted results showed that the earthquake occurred on the southern wall of Dacaidan-zongwulongshan fault with a strike of 107.19° and a dip of 56.57°,which is dominated by thrust movement with a little right-lateral strike-slip component.Most of the slip is observed at a depth of 10-20 km,and the maximal slip is 0.51 m.The inverted geodetic moment is 4.3×1018 Nm.