Abstract: The microstructure and properties of high chromium cast steel roll were studied to solve the serious thermal fatigue (TF) cracks in the surface of the roll. The relationship between TF cycles and main TF crack length was obtained by self-constrained TF tests and stretching tests at high temperatures. The mechanical properties at high temperatures were measured. The effect of microstructure and segregation on TF crack propagation was analyzed by SEM and EDS. The results showed that the route and manner of TF cracks initiation and propagation depend on the surface appearance of the roll. The speed of crack propagation is related to the high limit of temperature and heating speed of thermal cycles. In addition, TF performance is affected by the roll properties and microstructure change.