Density functional theory (DFT)is used to study the thermodynamics of formaldehyde removal under dielectric barrier discharges (DBD)non-thermal plasma (NTP)conditions at atmospheric pressure and ambient temperature. A calculation model is defined. The calculated reaction relative energies in this work confirm that the DBD plasma is effective for formaldehyde reduction at ambient conditions and at 1 atm. Present calculations indicate that the reactions of HCHO with primary free radicals such as OH·，O·，and H· are all thermodynamically favored. Moreover，theoretical results show that the main routes of O radical generation from O2 are direct dissociation and dissociative attachment-releasing electron, and the main pathways of H· and OH· from H2O are dissociation and attachment. The only thermodynamic obstacle to HO2· formation is 2H2O→H2O2+H2. The reactions of HO2· with other radicals are all thermodynamically favored. Comparative results between the previous investigation and the present work demonstrate that theoretical calculation with DFT can be an efficient and reliable supplement for experimental research.