Abstract: Dissolved gas analysis in transformer oil is one of the effective methods to evaluate the insulation performance of the transformer and ensure the safe and stable operation of equipment.In this paper,the first principles method is used to study the adsorption and sensing performance of copper-doped zinc oxide (Cu-ZnO) for single gas molecules (CO₂,H₂,and CH₄) in transformer oil.And the feasibility and application prospect of this sensing material for detecting three gases are deeply analyzed:study the doping behavior of Cu atom on the surface of Zn O;study the adsorption behavior of Cu-ZnO to a single gas molecule and the changes in the band structure,density of states and work function of Cu-ZnO after adsorption.The results show that Cu-ZnO is physically adsorbed to three gases:H₂(-0.221 e V),CH₄(-0.148 e V),and CO₂(-0.340 e V);after the three gases are adsorbed,the band gap of Cu-Zn O is changed somewhat,and all showed a decreasing trend,but the change of WF after CO₂ adsorption is opposite to that of H₂ and CH₄,indicating that it provides the possibility to selectively detect CO₂,CH₄,and H₂ as a field-effect transistor sensor.All the content in this article provides theoretical guidance for the use of Cu-ZnO as a gas-sensitive sensing material for the detection of dissolved gas in transformer oil and the evaluation of equipment insulation operation status.