Abstract: A method of obtaining the surface form deviation of the plane optical element by using BP neural network is presented. The curvatures of the interference fringes and the values of the fringe spacing of tested zones in the interferogram are determined, and the BP neural network is trained to obtain the value of light ring of the plane optical element. It is found that the test results obtained by Zygo interferometer are consistent with the test results obtained by the proposed method. Experimental results show that the method can enhance the adaptation capability of processing the interferograms and improve the measuring precision of the plane optical element