The experiments on NO reduction by the reburning of pulverized Yanzhou bituminous coal were conducted separately with different amounts of water vapor added in a fixedbed reactor，through which the effect of water vapor on NO reduction by pulverized coal reburning was studiedIt is found that NO reduction by pulverized coal reburning was accelerated by adding water vapor，but NO reduction per unit mass of coal decreased with the increase of water vapor since the burnout of pulverized coal was also accelerated at the same timeMoreover，the rates of CO production，CO2 production and O2 consumption were increased separately by water vapor，and CO2 production was promoted more significantly during the reaction stage dominated by volatile matter，but CO production was promoted more significantly during the reaction stage dominated by charHowever，CO2 production and O2 consumption decreased separately and CO production increased when they were counted by per unit mass of pulverized coalThe burnout time of coal reburning could become shorter with increasing water vapor，for example the burnout time was shortened by 25.9% at 2% water vapor，and was shortened by 47.8% at 4% water vaporAdding a certain amount of water vapor into the reburning zone could not only improve NO reduction by pulverized coal reburning but also increase burnout ratioThe optimum amount of water vapor could be obtained through experiments on the basis of coal properties of coal，NO concentration in the main combustion zone，the proportion of reburning coal，the excess air coefficient of the reburning zone，and economic appraisal in engineering practice.