Low load peak operation of coal-fired unit the flue gas temperature from the economizer outlet enters the SCR denitrification device is low, deviated from the temperature window of the denitrification catalyst, resulting in low efficiency of denitrification, even the denitrification system is not normal put into operation, resulting in the concentration of nitrogen oxides emission exceeded, has become the main factors restricting the unit’s depth peak capacity. This paper introduces several SCR inlet flue gas temperature upgrading technology for realizing the emission of NO_x of coal-fired unit, and compares the technical characteristics of each other, and provides reference for the power plant to carry out the whole working condition denitrification Reformation.