Polycarbonate (PC) is considered a promising substitute for insulating materials due to its excellent insulation and mechanical properties. The main cause for PC insulation aging is the breakage of chemical bonds at high temperatures. The reactive force field (ReaxFF) method is first employed in a molecular dynamics (MD) simulation of polycarbonate pyrolysis to elucidate the mechanism for thermal aging at the atomic level. The results show that the main reaction pathway for breakage of the polycarbonate main chain is C-O bond breakage of the terminal group or between PC monomers. CO2, CO, CH4, and H-2 are the major products generated following polycarbonate pyrolysis. The formation mechanisms of these dominant products are detailed for the first time based on the simulation trajectories. The activation energy and pre-exponential factor extracted from the ReaxFF simulations show good agreement with experimental results. The fracturing of the main chain and the production of small molecule gases both decrease the degree of polymerization of the polycarbonate, resulting in thermal aging. These results are fully consistent with previous experimental results. This work demonstrates that ReaxFF simulation is a feasible and reliable method for elucidating detailed chemical reaction mechanisms in polycarbonate pyrolysis.