It has been found that catalytic activity can be promoted with the sintering of some platinum catalysts in some VOCs' catalytic combustion reactions. Hence, the pre-treatment for these catalysts is always carried out in reactant gas for several hours. Effects of pre-treatment atmosphere, the pre-treatment temperature and the reaction atmosphere on the sintering process were studied in this paper. The results show that the sintering can be observed at high reaction temperature (>523 K) in the reaction conditions. Water steam and reactant substance also plays an important role in the sintering. Moreover, the reaction kinetics parameters for the fresh and the used catalysts in the toluene combustion reaction were calculated with the Mars van Krevelen mechanism.