Perfluoropentanone (C5F10O) gas mixtures are expected to be used in gas-insulated switchgear due to their excellent environmental and insulating properties. Nevertheless, the study of the insulating properties and influencing factors of C5F10O gas mixtures under the internal conditions of gas-insulated switchgear is not yet comprehensive. This paper comprehensively investigates the insulating properties of C5F10O/ dry air gas mixtures. The findings demonstrate that adding C5F10O significantly enhances the insulating properties of the gas mixture. The findings of this research serve as a valuable reference for the engineering application, operation, and maintenance of C5F10O/dry air gas mixtures.