In this study, the adsorption behavior of CuO-GeSe, NiO-GeSe, and Ag2O-GeSe towards the main dissolved gases CO, CH4, C2H2, and C2H4 in transformer oil was systematically studied based on DFT. The adsorption structure, band structure, density of states, deformation charge density, and molecular orbit were analyzed to explore the interaction between the modified monolayers and gases. The results show that the adsorption of the four target gases on pristine GeSe belongs to weak physical adsorption. Metal oxides modification improves the conductivity of GeSe, and the formation of numerous triangular structures makes the modified substrates hard to deform during gas adsorption. Due to the poor gas sensitivity and extremely short recovery time of CH4 on CuO-GeSe, NiO-GeSe, and Ag2O-GeSe, these three modified structures are not suitable to be used as a material for detecting CH4. The conductivity of MO-GeSe changes in different degrees after adsorbing CO, C2H2, and C2H4. The gases can be detected according to the different change rule of conductivity upon adsorption. In addition, gas desorption from the substrate can be achieved by controlling the temperature. This study provides a theoretical basis for the application of gas sensors used in DGA.