The EuLX-ray emission from the impact of Eu20+ ions of 3.0-6.0 MeV kinetic energies on Au target is detected. We obtain the experimental relationship of single ion X-ray yield with kinetic energy of ions. Considering the ion stopping in the target, the yield of the single ionLshell holes produced by the collision of Eu20+ ion with Au atom is calculated. According to the fluorescence yield of EuLshell holes, we deduce the theoretical relationship of X-ray yields with kinetic energy of ion. The results show that the theoretical curve is well consistent with the experimental data.