Abstract. Interferometric Synthetic Aperture Radar (InSAR) has shown unique capabilities in numerous applications for deformation monitoring. However, InSAR will lose effectiveness with large-gradient deformation due to the limitation of maximum detectable phase gradient and the phase unwrapping step of InSAR. Coalfield is the exact object providing such challenges for InSAR technique. Strong mining activities often induces large scale non-linear deformation with large gradient. This paper integrates offset tracking technique based on Corner Reflector (CR) and InSAR to overcome relevant problems. By applying offset tracking to high resolution TerraSAR-X intensity images, the coarse estimation of large deformation was obtained and extracted, allowing the following InSAR processing to carry out phase unwrapping correctly. Finally, the fine estimation of deformation was done by the Persistent Scatterer InSAR (PSI) technique. The detected deformation time series indicated good root-mean-square errors (RMSE), validated by GPS in situ investigation. All InSAR data were processed in the open source software StaMPS and one in-house InSAR package.