Abstract: Research on dissolved gas sensing in transformer protection is of great significance for ensuring the safe operation of power systems and reducing the operation risks of oil-filled transformers. Based on first-principles calculations, this paper investigates the adsorption characteristics of four dissolved gases (CO, CO?, H? and CH?) in transformer oil on the surfaces of pristine and Rh-modified WSe? monolayers. The results show that Rh atom doping can reduce the band gap of WSe? and improve its gas sensing performance. Analyses of charge transfer, deformation charge density, density of states, band structure and recovery time reveal that the Rh-WSe? system exhibits excellent adsorption capacity and sensing performance for H?. At room temperature of 298 K, its recovery time is only 4.79 s, enabling repeated detection at ambient temperature, which makes it an ideal hydrogen-sensitive material. This study provides a theoretical basis for the application of Rh-doped WSe? in transformer fault detection.