In recent years, the velocity dependence of the damage cross section, the damage efficiency and the damage morphology of solid materials induced by swift heavy ions, named ion velocity effect, is observed. But the mechanism or origin of the ion velocity effect is not clear up to now. In this paper, the discovery, current researching situation and some typical experimental results of ion velocity effect in the process of the damage creation in solids induced by swift heavy ion irradiations were briefly described, and the main theoretical explanation of ion velocity effect was also reviewed and discussed in short words.