Pyrolysis and gasification of wastes supposed to be in an entrained gasifier were analyzed by thermogravimetry under a constant heating rate of 2 K/min. Ordinary plastics PE, PP, PS, and PET are rapidly decomposed in the temperature range of 600-750 K, and PVC and rubber are decomposed in the range of 500-800 K. Sawing tip and cellulose are pyrolyzed in the range of 550-800 K, and municipal waste and waste plastics are in the range of 500-800 K. Gasification of char with CO2 and/or H2O proceeds in the temperature range of 1,000-1,500 K and the TG curves are dependent on the char components. It is shown that the degradation processes of PVC and rubber are divided into two or three stages. The respective TG curves of individual materials are well simulated by modified volume reaction model equations. The reaction rate constants and the related activated energies and pre-exponential factors are determined from model equations. TG curves of the waste plastic and municipal waste are well simulated by adding the reaction ratios of individual components.