Abstract: The influence of superheat on internal structure of the bearing steel is researched by the macrostructure inspection tech-nology of dendrite corrosion and metallographic test method of bloom and wire with quenching and tempering heat treatment. The re-sults show that the equiaxed crystal ratio of the low superheat process increase. The secondary dendrite spacing decreases. Internal metallurgical defects such as segregation, shrinkage cavity improve. But there is little difference in the wire rod pickling macrostructure and carbide nonhomogeneity. Segregation control in the mixed crystal area is more serious than that in equiaxed crystal area. And there are a large numble of large size eutectic carbides.