Abstract: When coal-fired units participate in the deep peak regulation, the units are in low-load operating conditions for a long time, resulting in flue gas temperatures deviating from the normal operating range of denitrification device and excessive NO_x emissions. In this paper, the wide load denitrification technologies are sorted out. The selective catalytic reduction （SCR） denitrification transformation schemes are analyzed from the catalyst side, ammonia spraying side, combustion side, flue gas side, and feed water side. The replacement of high-performance wide-temperature denitration catalyst and intelligent fine ammonia injection are the trends to realize the optimal operation of SCR. The selective non-catalytic reduction （SNCR） transformation schemes are analyzed in terms of flue gas circulation, adjustment of spray gun position and addition of wide temperature additive, and the three transformation schemes are conducive to improving the denitrification performance under low load. Combined denitrification technology can improve unit flexibility. Among them, the combined SNCR and SCR denitrification technology of the circulating fluidized bed boiler can meet the denitrification requirements of the unit under 30%−100% load. The combined denitrification technology of the pulverized coal furnace can improve the denitrification efficiency and reduce the investment cost. Ozone combined SNCR and SCR denitrification technology can further improve the denitrification efficiency and improve the adaptability of the denitrification system.