NO reduction by lean coal chars with emphasis on the effect of adding the catalyst KOH to the chars on the NO reduction efficiency was studied. The experiments were conducted in a drop-tube furnace at temperatures of 1173-1323 K under fuel-rich conditions. Experimental data for the NO reduction efficiency obtained by using the lean coal chars containing different KOH contents are compared and, thus, the effort of KOH addition on the NO reduction can be revealed. Experimental results show that the NO reduction ability of the original lean coal char is very poor, but the NO reduction efficiency can be enhanced appreciably when KOH is added into the char. This can be explained by the fact that KOH can strongly catalyze the NO reduction by the lead coal char under fuel-rich conditions. Gas temperature and oxygen concentration in the reaction area are also shown to be important parameters influencing the NO reduction.