Abstract: High temperature properties of continuous casting high carbon steels were measured by tensile tests with a Gleeble 1500 system and two embrittlement temperature regions of region Ⅰ and region Ⅲ were found. The results indicated that the cause of embrittlement in region I was the existence of liquid film along dendritic interfaces, and the embrittlement in region Ⅲ was caused by precipitation of proeutectoid ferrite film along austenite grain boundary. AIN precipitation at the full austenite grain boundary would worsen the ductility of the steels.