A new method for conversing the spatial amplitude distribution of a given image into its spatially similar phase distribution was proposed.The implementation of the present method can be based on the double exposure photorefractive holographic phase-shifting interferometry,in which the optical 4-f system with an amplitude-only spatial light modulator(SLM) as the image input device and with the photorefractive crystals as holographic recording medium was employed.We present the fundamental idea on which the method is based and verify its effectiveness and correctness by experimental result.