Abstract: To determine the causative fault slip distribution of the Tohoku M_W9.0 earthquake in Japan， the coseismic deformation field of this earthquake was obtained with synthetic aperture radar interferometry (InSAR) technique based on Envisat/ASAR data. With detailed analysis and comparison of different methods used to resample InSAR deformation data， the fringe rate method taking into account spatial coherence of the interferogram was chosen for data resampling. Based on the elastic half-space dislocation model， the slip distribution of causative fault was inverted from InSAR and GPS data using the least squares method. The research results show that the fringe rate with coherence method is more suitable for data resampling of wider range InSAR deformation field, within which there are finite boundaries except fault. The majority of the fault slips occurred mainly in the range of 50 km below the surface， and the maximal slip on the fault is 49.9 m， meanwhile， the moment tensor is 4.89×10²² N·m， the corresponding moment magnitude is M_W9.1. All these are consistent well with the results from seismological inversion， suggesting this inversion result in this study is reliable.