Abstract: Hot cracks occurred on the friction surface of a SiCp/Al composite brake disc during the bench test of harsh load condition. Aiming at the cracks on the friction surface of the SiCp/Al brake disc after bench test, a failure analysis method combining test and simulation was adopted. An MTS Landmark servo hydraulic test system, a Brinell hardness tester, a scanning electron microscope, a metallographic microscope and a high-precision industrial CT scanning device were used to carry out mechanical properties testing, microscopic analysis of cracks, fracture analysis and crack CT scanning of the brake disc, respectively. In addition, from the perspectives of service and forming of the brake disc, braking thermal simulation and forming process simulation were carried out, respectively. The results show that mechanical properties deterioration of the brake disc after harsh bench test and large stress generated by the harsh braking condition are the main factors for the formation of cracks in the brake disc during the bench test. At the same time, holes and inclusions had an inducing and guiding effect on the initiation and propagation of cracks. The tip and segregation of SiC particles tend to induce the damage of matrix material, and aggravate the initiation and propagation of micro-cracks. By clarifying the formation mechanism and causes of brake disc cracks, a scientific basis can be provided for the forming quality control of brake discs, and an improvement direction can be pointed out for the future application of aluminum matrix composite brake discs in trains of higher speed grades.