Abstract: The online monitoring technology of transformers is a crucial guarantee for the construction of global energy internet,and the diagnosis of dissolved gases in transformer oil is considered an effective criterion for transformer faults.The adsorption process of six dissolved gases on C₃N nanosheets modified with Pt is simulated using density functional theory method.The study reveals the relevant adsorption and sensing mechanisms through calculations of band structure,density of states,differential charge density.The results indicate that Pt modification significantly enhances the gas-sensing response of C₃N nanosheets,especially in capturing CO and C₂H₂gases.This enhancement is primarily attributed to the contribution of the d orbital electrons of doped metal particle.The adsorption capacity of Pt-modified C₃N nanosheets for dissolved gases in transformer oil is ranked as:CO＞C₂H₂＞C₂H₄＞H₂＞CO₂＞CH₄.And the electronic properties of the adsorption substrate change significantly.This work provides a theoretical basis for the experimental development of high-performance gas-sensing sensors for detecting dissolved gases in transformer oil.