This report describes the thermal decomposition behavior and the formation to investigate the flame-retardant mechanism of organic metal salt in polycarbonate. Moreover, the flame retardancy of the polycarbonate with the addition of various kinds of organic metal salt was evaluated, and the difference in flame retardancy was considered. The decomposition of organic metal salt in polycarbonate during combustion promotes the decomposition of polycarbonate as a catalyst and the formation of a char layer on the surface that inhibits the supply of flammable gas and heat transfer. The flame retardancy is related to the final decomposition temperature of organic metal salt, and it is highest when it is close to the maximum decomposition temperature of polycarbonate. (C) 2004 Wiley Periodicals.