A study of rare earth effects on inclusion modality of 8Cr4MoV cold work roll steels was carried out in the laboratory, the steels smelting by a 50kg vacuum induction furnace, atmospheric casting, processing sample after annealing, then inspecting the steelsmicrostructure, inclusion modality and composition; The results showed that the steels microstructure fine, micro-hardness increased with increasing rare earth content, while the average size of inclusions decreased significantly, also the morphology and composition of inclusions significantly changed from the angular black manganese sulfide to the ball white sulfur oxides of rare earth, and thus played roles of deoxidation, destulfufization, purification and deterioration of liquid steel, it will help improving the fatigue performance of the work roll.