Abstract: In recent years, the strategic objective of achieving "carbon peak and carbon neutrality" has been established, aiming to substantially reduce greenhouse gas emissions and promote a comprehensive green transformation of economic and social systems. The new generation of environmentally friendly ring main unit (RMU) is progressively replacing conventional SF₆ RMU. The SF₆ RMU has been already phased out in the "Standardized Design Scheme for 12 kV Distribution Cabinets (Boxes)" of State Grid. And the updated technical requirements for the isolation design of environmentally friendly RMU has been introduced. Thence, the research and practical application of a high-voltage environmentally friendly RMU interlock device have been primarily reported. Importantly, the device incorporates both mechanical and electrical interlocking device, effectively resolving the interlocking challenges posed by the new isolation requirements for environmentally friendly gas-insulated switchgear (GIS) ring main units (RMUs). With its compact and simple design, it offers ease of installation and operation, and demonstrates high adaptability to a wide range of interlocking configurations in switchgear applications.