Abstract: In order to prepare high-efficiency denitrification agent with activated carbon as carrier,activated carbon was modified by ultrasonic in cooperation with HNO3,the influence of modification time,temperature,acid concentration,and ultrasonic power on the structure and surface properties of activated carbon had been investigated systematically.By ultrasonic acidization at low temperature of 313 K,the number and surface area of the micropores (0.4～0.5 nm)were oriented to increase.Differently,the micropores and mesopores (2～10 nm)were developed by treating 25 minutes at 343 K.However,when the treating time was increased to 75 minutes at 343 K,the mesoporous structure was oriented development.When the number of mesopores(2～10 nm)was increased,it was more advantageous to increase the adsorption capacity of molecules such as N2 and I-3.With the increase of nitric acid modification time,temperature,concentration and ultrasonic power,the adsorption amount of I-3 increased first and then decreased.Under the modified conditions of 75 min,343 K,acid concentration of 7.0 mol/L and power of 80 W,I-3 adsorption was the best.The denitration catalyst for removing NO in flue gas was prepared by loaded with NH4VO3 on the modified activated carbon,and the denitrification rate stabilized at 55%,which was 2.5 times than that of the origina.