NOx is a significant atmospheric pollutant triggering haze weather. The existing DeNO(x) technology has drawbacks of needing additional reducing agent and high working temperature. In order to overcome those defects, a novel La0.6Sr0.4Fe0.8Mn0.2O3 (LSFM)-modified gas diffusion electrode (GDE) was prepared to establish an in-situ electrochemical DeNO(x) process. The DeNO(x) efficiency was enhanced by increasing Nafion and polytetrafluoroethylene (PTFE) content in the GDE within an appropriate range. Nafion created the proton transport pathway of electrolyte-Nafion-three phase interfaces (TPIs) and PTFE improved the hydrophobic gas channels. The highest DeNO(x) efficiency of 71.1% was obtained with inlet NOx of 1000 ppm under ambient temperature (25 degrees C) when the mass ratio of LSFM:Nafion:PTFE was 1:0.117:0.23. In the electrochemical DeNO(x) process, i) NOx was absorbed by the gas diffusion layer and then transferred to the catalyst layer through the hydrophobic channels; ii) NOx was electrochemically decomposed to N-2 and O2- under the catalysis of LSFM; iii) O2- was transformed to OH- on the TPIs by combining with H(+ )and oxidized to O-2 in the anode. Simultaneously N2 was released. Its advantages of no reducing agent, mild operating condition and high energy-efficiency indicate great potential for practical application.