Abstract: The type,distribution,morphology and constituents of carbide in the as-cast high speed steels (HSSs) for roller were studied by XRD,SEM and EDS.The volume fraction of carbides in the alloys was measured.The effects of carbides on as-cast microstructure of HSSs for roller,the relationship of the composition of alloy with the type and the volume fraction of carbide were analysed.The as-cast microstructure of HSSs for roller consisted of martensitic matrix,a small amount of retained austenite and MC,M6C and M2C carbides.The most important microstructural factor of HSSs for roller was MC carbides.The volume fraction of carbides increased as the carbon content in the alloy increased,and to a certain extent,was affected by tungsten equivalent.