A new theoretical analysis is given to the divide／combine polarization—induced—fading eliminated technique of an interfcrometrie fiber—optic sensor and its array,and a new way is proposed to realize the real tline detection of the divide~combine method by squaring each signal and adding them togeter. The maximum amplitude fluctuation of this method is calculated. and the conclusion is drawn that three is the best number of the analysers. According to the analysers, the sarisfactory experimental result is achieved on the Mach—Zehnder interferometer, and the application of the method in the interferometric array is designed.