By coupling microwave heating with the catalytic action of a catalyst, the purification of simulated automotive exhaust was investigated over a noble metal catalyst. The effects of microwave heating on the lighting-off temperature and operation window were observed. By comparing the activity of the catalyst in the microwave heating mode with that in the conventional heating mode, it was found that microwave heating caused the lighting-off temperature of the catalyst to decrease remarkably. Even when 10% of H2O was added to the simulated exhaust, the lighting-off temperature could still be lowered more than 50degreesC. Meanwhile, the activity of the catalyst increased greatly at the low reaction temperatures, and the operation window was also enlarged, obviously by microwave irradiation.