The prediction of PIMP is very important in the research of microwave and RF PIM.The effects of PIM noise in devices or systems can be directly observed. Using the method of IM Microscope, many problems that can't be solved by other methods can be handled. In this paper,an improved method on the base of IM Microscope is described. The model of output signal amplitude and phase distortion is introduced and the detailed math models are presented. By using this method many measurements in laboratory can be reduced.