Abstract: Aiming at crackle occurs of the drum brake during the braking process, the contact analysis model and transient thermal analysis model of the drum brake is established respectively based on the finite element method and the non-static equation of heat conduction. The magnitude and the distribution of mechanical stress as a result of the brake shoe's braking on the drum is analyzed by nonlinear-contact method. The magnitude and the distribution law of heat generation, heat dissipating and the thermal strees is given by the method of transient thermal analysis. The cracking reason of the brake drum of a certain heavy vehicle is analyzed. It show that either the mechanical stress or the thermal stress can influence the brake drum's cracking under the emergency braking condition, yet the influences of morphology of cracking in the dram are different. The conclusion is also validated by the practical cracking morphology of the brake drum, proving that this method has good value in the field of engineering application and significance of theoretical guiding.