The increase of the plastic wastes has urged finding different solutions for their recycling. Thermal pyrolysis is a suitable solution for refining the combination of different plastics. The main goal of this research is developing a model to predict the distribution of products obtained from pyrolysis. To do this a mechanism model based on free radical mechanism is developed. In this model some kinetic stages are used including initiation, scission, abstraction, aromatic making and radical combination. After determining the kinetic constants, the equations were solved in MATLAB software. The results were compared with experimental results from a conical spouted bed reactor (CSBR) in temperature (500–900 °C) and residence time (0.016–0.032 s). the results show that the model can predict the experimental observation for different temperatures and residence time and estimate the amount of low and high density products in a way that the increase of that gas fraction increase and high density products decrease. Also in all the situation the amount of olefin fraction is more than paraffin and diolefin.