The effects of ash on the abrasion and blocking of DeNitration Catalysts are introduced in coalfired power plant. It is shown that the ash abrasion on the catalyst is powerful based on analyzing the ash characteristics. In order to get rid of the coarse ash particle, reduce the abrasion and blocking on the catalyst, and prolong the catalyst service life, it is proposed to install the ash hopper and enlarge the flue section before SCR(selective catalytic reduction).