Abstract: Theoretical analysis of ICF shell X-ray radiography mechanism and the derived digital image’s profile edge forming is carried out. In order to determine the center and radius of the microsphere accurately, the least square fitting expressions with some characteristic points on the shell edge is deduced. For shell image edges of different types (step-shaped or roof-like), the average second-order derivative algorithm or the least square Lorentz fitting peak-finding algorithm of radial absorption intensity is used to obtain the ICF shells’ circumferential edge data with a sub-pixel accuracy. The power spectra curve as a function of the mode number of outer or inner profiles are also calculated by the application of fast Fourier transform to the circumferential profile data.