This paper is devoted to the modeling of the pyrolysis process in order to predict mass and heat loss profiles of a used tire sample. After making certain assumptions, the thermal balances and kinetics of each reaction were written. The resolution of the differential equations allowed us to present the profile of heat variation within the sample as a function of time. The conversion of the reaction was also modeled and compared with that obtained experimentally. There is a satisfactory agreement between the theoretical and the experimental results. The modeling is based on the energy behavior of each reaction and showed in particular that certain exothermic reactions intervene during the pyrolysis of the used tires.