Abstract: In order to achieve NO_x emission standard of circulating fluidized bed( CFB) boiler,the current NO_x control method and application in China were described.Taking urea and ammonia as the reducing agents,and combining with CFB boiler denitration situation in a certain power plant in northwest of China,the principle,main SNCR denitration process flow and equipment were introduced.Besides,the advantages of SNCR denitration in 300 MW CFB boiler were analyzed.Combined with the characteristics of CFB boiler,the original SNCR equipment was modified and then the modified effect was analyze.The results show that,the action of reducing agent regulating valve is obviously more accurate and NO_x emission is more stable by adjusting the position of measuring points and optimizing control logic.The injection mode of horizontal flue is changed from horizontal twine to staggered twine,with a distance of 0.3 m staggered,so that more flue gas can contact with the reducing agent and improve reaction efficiency.By changing the operation mode,reducing the primary air volume and increasing the supply of secondary air,the original NO_x emissions can be reduced by 10%.After the modification,SNCR denitration device can control the NO_x emission value below 50 mg/Nm~3( calculated by NO2 and converted to 6% O_2 concentration),and denitration efficiency is higher than 85%.At the same time,the ammonia nitrogen ratio is not higher than 1.8,and ammonia escape value is reduced from 7×10~(-6) to 3×10~(-6),which can effectively improve the denitration efficiency and system stability.