In order to prolong the life of inner liner of coke can, the thermal fatigue property of Cr17Mn10Ni3 heat-resisting steel was analyzed and studied from cast metallurgical structure, the morphology of crack surface and cross-section, the injury factor by OM, SEM, photoshop and imagetool software. The results shows, Cr17Mn10Ni3 has a good thermal fatigue property because of the microstructure with good thermal conductivity, austenite matrix and break carbide lying in treelike crystals. It decreases the innerstress and postpones the time of crack formation and extension, during the process with 1100°C and room- temperature water cooling. The cracks mainly appear in the phase interfaces between carbides and matrix, ferrite and austenite, and grain boundaries. The thin and deep cracks with high concentration are beneficial to relax the elastic strain energy. But a single and thick crack easily widens and deepens to be detrimental to the thermal fatigue property.