A transient heat transfer and thermal stress analysis for a brake drum of commercial vehicles have been performed by ANSYS code in the cases of single braking and the repeated braking condition. The temperature and thermal stress distributions in the brake drum under various braking conditions were obtained using a two-dimensional axisymmetric model. In case of deceleration of 0.3G with an initial vehicle speed of 60km/h, the maximum temperature in the drum was $87.6^{circ}C$ after braking application. The maximum stress of 78.7MPa in the drum occurred at the intersection between the flange and hat under a condition in which repeated 15 cycles braking with an initial vehicle speed of 60km/h and a deceleration of 0.3G is applied to according to KS R1129. The maximum stress value is much lower than the yield strength of drum material(FC250).