The principle of the coded imaging and its decoding in inertial confinement fusion is described simply in this paper. We take ring aperture microscope for example and use backproject　(BP) algorithm to decode the coded image. The　decoding program has been performed for numerical simulation. Simulationts of two models are made, and the results show that the accurance of BP algorithm is high and effect of reconstruction is good. Thus,it indicates that BP algorithm is applicable to decoding for coded image in ICF experiments.