Denitrification in power plants is an important means to prevent and control NOx. The application of fly ash after denitrification requires more technical research. In this paper, the effects of denitrification fly ash on the standard consistency, setting time, expansion and strength of cement mortarwere are studied and compared with those of non-denitrification fly ash. The results show that addition of denitrification fly ash can reduce the standard consistency of cement, slightly prolongs the initial setting time and shorten the final setting time.While the expansion of cement mortar with denitrification fly ash increases, and the loss is more obvious than that of fly ash without denitrification. With the increase of denitrification ash content, the 3d and 7d flexural and compressive strength of cement decreases, and the later strength increases, but it is inferior to that of non-denitrification fly ash.