We propose a new approach for determining the distribution of full-field refractive index based on the angle deviation method (ADM) with a surface plasmon resonance (SPR) sensor in phase detection. The inhomogeneous distribution of refractive index causes the variant deviation angles in the test light. SPR sensor is a sensitive angular sensor especially for phase detection. For the full–field phase measurement, we should use the four-step phase shift interferometry (PSI) to measure the phase shift profile of the test light after reflected from the SPR sensor. Thus the phase shift is caused by the variation of the refractive index. The approach can plot the full-field refractive index distribution in a short time and its resolution can be better than 2.2×10-8 (RIU).