We present a new method for inverting coseismic slip distribution based on arc measurements of InSAR inter ferograms. The method only solves the integer ambiguities on the selected arcs so that the challenging task from global unwrapping of low coherence interferograms can be avoided. The simulated experiment results show that the new method recovered the given slip distribution well at different coherence quality levels. However, the conventional method with global interferogram unwrapping fails when the interferogram has some isolated areas. In addition, the new method is capable of using surface rupture offset data gathered in the field. We apply the proposed method to study the 2010 Yushu, China Ms 7.1 earthquake. Inclusion of field data can help to enhance the results of fault slip inversion. It derives a maximum slip of ∼ 3 m, larger than the published coseismic slip results on this event, but agreeing with the largest offset of 3.2 m from field investigation.