To find an effective way for reduction of NO_x emission, this paper made use of a tube furnace to discuss the effects of residence time, temperature, and different catalysts on char-NO reactions. The particle size of char is 1.7～2.8 mm. The results show that the extending residence time is not conducive to the reduction of NO below 900 ℃, and the residence time has a few effects on the reaction at 900 ℃. With the increase of charring temperature, the reactivity for large char tends to be decreasing. But the principle is the opposite pattern—a rising trend in the range form 500 ℃ to 600 ℃. Adding different types of metal catalysts can promote the reduction of NO, the average order of the catalytic activity is Fe>Cu>K>Na>Ca>Mg. The catalytic effect of metal elements in char is affected significantly by temperature, and the metal catalytic ability is different in different experimental conditions. Besides, the characteristics (including volatile content, pore structure and crystalline structure) of char have a great influence on the char-NO reactions. With the higher volatile content, the more developed pore and the lower degree of graphitization, the reduction effect of NO is better.