This paper reports our experimental results obtained by using high-purity LiNbO3 for photorefraotive effect which is induced by YAG:Na3+ laser beam. The spatial distribution of birefractive change have been measured. It is demonstrated that the spatial distribution of birefringence change is asymmetric. A plot of the photorefraotive as a function of various annealing temperatures and hold time have been measured. The induced changes in extraordinary Is 3-4 times as large as the ordinary index.