Reaction pathways and specific mechanism of NO removal by non-thermal plasma (NTP) were for the first time investigated via FT-IR measurements. It was found that NO removal was attributed to a co-effect of N and O radicals but centered on the latter, and only O radical worked for NO oxidizing to NO2, since O-3 can't be obtained under the lock of fast NOx reaction. O-2 content regulated reaction behaviors that reduction pathways was dominating when O-2 content was < 4% while oxidation pathways under 4-21%. NO was mainly oxidized to NO2 when in O-2 content of 4% to 10%, thanks to fast NOx reaction. While under other O-2 content, fast NOx reaction was broken and NO would be further oxidized to N2O5 and HNO3 totally, followed by the generation of O-3 from background. NO and NO2 would be obtained again from background reactions when high O-2 content under high SIE, along with disappearance of O-3. Furthermore, the electrode temperature (> 30 degrees C) and the addition of flue gas components like H2O, CO and CO2 showed negative effects on NO removal, while HCl were on the contrary. SO2 revealed nearly no influence.