A new technique for reconstructing three dimensional refractive index field was proposed, which utilized a confocal system to scan the reconstructed holographic interferogram of a measured object in three dimension, and the recorded interference intensity was processed to obtain three dimensional refractive index field. For this method, the mechanism is very simple, and the multidirectional holographic interferometric scan and complex reconstruction algorithm are not needed, also not interfere the measured field and is a non-intrusive measurement method. The priliminary experimental result was given to demonstrate the feasibility of this method.