Selective Non Catalytic Reduction (SNCR) denitrification technology is one of the most important technology for denitration from coal-fired industrial boilers. The NOx removal efficiency of SNCR in the utility boiler is generally low. And few work has been done to study on the SNCR from industrial boilers. In the study, the temperature inside the chamber of the furnace and the NOx emission concentration with different spray gun positions, the hydraulic pressure and the gas pressure were measured for a 20 t/h entrained-flow boiler, and the denitrification performance of SNCR in an entrained flow bed coal powder industrial boiler was studied. The results show that the temperature window of SNCR using urea is range of 790-850 ℃, which is located around the central region of the furnace. The better NOx removal efficiency can be achieved with the spray gun on the centre of the side wall in comparison with that on the top of the furnace. The depth and angel of the spray gun inside the furnace have less influence on the NOx removal efficiency. When the spray gun is located the best position, the NOx emission concentrion is 38 mg/m3 with NOx removal efficiency of 87.2%, satisfying the ultra-low emission standard. The flow rate of the spray gun increases with the increase of the hydraulic pressure or the decrease of the gas pressure. When the hydraulic pressure is larger than the gas pressure, the excellent atomization can be obtained and the small liquid droplet can be uniform distributed like a fan. When the ammonia-nitrogen molar ratio is larger than 2.38 and less than 3.00, the lower the hydraulic pressure is, the higher the denitrification efficiency is. The SNCR denitrification efficiency is higher and ammonia escape is less with hydraulic pressure larger than 0.30 MPa and less than 0.35 MPa，as well as gas pressure greater than 0.29 MPa and lower than 0.40 MPa. The homogeneous droplet size distribution and the uniform spatial distribution have more important impact on the NOx removal efficiency than that of the sector angle.