Abstract: In order to study and predict the fire behavior of polymers under unilateral heating conditions, the transient heat transfer and pyrolysis gas transport processes were considered, and the pyrolysis and combustion processes of polymers were described from two aspects of energy and mass according to the thermochemical reaction mechanism, the polymer pyrolysis model was established, and the fire response prediction method was proposed. The mass loss and heat release rate of polycarbonate were predicted, and the pyrolysis and carbonization of the material at different depths under the unilateral heat flow of 50 kW/m² were investigated. The results show that the model can effectively predict the mass loss and heat release characteristics of polycarbonate. Under different temperature rise rate and heat flux, the values of peak mass loss rate and soaking heat release rate calculated by the model agree well with the experimental results, and the errors are lower than 6.0% and 5.0%, respectively. Compared with the average heat release rate at 50kW/m², the predicted average heat release rate at 75 kW/m² and 92 kW/m² is increased by 14.6% and 27.4%, respectively.