Brake system is the most important system in the vehicle considering the overall vehicle safety and speed control. Brake applications are repetitive during a city traffic and hilly terrain on downhill gradient. Frequent braking gives rise to an overheating of the brake drum and its components. Braking operations at high temperature gives rise to problems like reduced deceleration due to loss of brake pad friction characteristics, pad softening and sticking to drum, pad distortion and wear etc. All these factors collectively result in deterioration of the braking performance and reduction of brake pad durability with time.Till date most of the thermal analysis performed for brake drum heating are through physical testing using brake system prototypes and by means of CFD tools. These methods are time consuming and expensive. There is a need for an alternative method to reduce physical trials and prototype building and reduce dependency on CFD analysis. The present paper focuses on developing 1D mathematical model of drum brake system using Model Based Design (MBD) approach. By MBD methodology, the entire mathematical model is built by discretizing every component of brake system in finite metal masses connected with relevant heat transfer units. These units characterize the different modes of heat transfer viz conduction, convection and radiation. Convective heat transfer variation over drum and pad surfaces based on the change in vehicle speed is also accounted. The model simulates the temperature variations at different locations within the brake drum assembly. It is capable of simulating temperature change for various duty cycle profiles accounting change in brake energy due to vehicle speed. This model can be used in predicting temperature variation in the early stages of brake system design enabling the possibility of optimizing system for specific requirement.