A real time holographic testing method of transparent objects by using the interference pattern formed by the reconstruction of the reference wave and the original reference wave is introduced. The above interference fringe pattern is proved to be similar to the pattern which is formed by the reconstruction of the initial object wave and the wave scattered by the object during observation. The principle of this method and the characteristic function of the contrast of the interference pattern are presented. The phase distortion caused by any optical element in object optical path can be eliminated and the unexpected light emitted by the under testing object itself can be also avoided by using this method.