Abstract: Basic principles and physical mechanism of image measurement by using imaging plates(IPs) are studied in this paper, and fundamental problems about applications of the IPs in gamma-ray image measurement are also analyzed. Monte Carlo models of imaging plates in common use are built, involving three types of IPs, i.e. MS, SR, TR. And the energy deposition of gamma rays of different energies in the IPs are calculated through the MCNPX code and the NPE code based on a Geant4 platform. As a result, the energy deposition of SR-type and MS-type IPs is 3-5 times larger than that of TR-type IPs in the low energy part, and 7-9 times larger in the high energy part. The theoretical and experimental results of the relation between gamma-ray sensitivity of MS-type IPs and copper foil thickness agree well with each other. The spatial resolution of IPs in gamma-ray imaging is better than 50 m.