To improve the thermal fatigue performance of brake disks, we prepared an Fe-based coating on the cast steel material for the brake disks using laser cladding technique, and then analyzed the crack growth rate and microstructure evolution of the cladding layer and matrix material during thermal fatigue using optical microscope and scanning electron microscope. Results show that the microstructure of the laser cladding layer exhibited severe segregation. In the thermal cycle process, the supersaturated M₇C₃ became the rapid propagation channel of thermal fatigue cracks, thereby resulting in brittle fracture and poor thermal fatigue performance. Through heat treatment at 850 ℃ for 5 h, the element distribution was homogenized and dendrite segregation and internal stress were eliminated. Moreover, M₇C₃ transformed into M₂₃C₆ with relatively stable high temperature performance, which remarkably optimizes the thermal fatigue performance of the cladding layer. No macrocracks were observed on heat-treated cladding sample after 2000 thermal fatigue tests, and its thermal fatigue properties were considerably better than those of the matrix materials.