In this paper, the Xray radiograph technology, which is used for wallthickness measurement of multilayer plastic microsphere, is expounded in detail. The mechanism that Xray is absorbed by the material of plastic shell used as a highgain target in ICF is investigated theoretically. The theoretical analysis and experiment prove that, in vacuum environment, the Xray tube works under 10kV voltage and outputs Xray of 8keV energy, the best image of shell with good contrast and clear interface can be obtained. This technique offers a good measuring method to the shells making.