The invention provides a ring main unit adapter. By means of the ring main unit adapter, cables are convenient to assemble and disassemble, and the maintenance power failure time of a ring main unit is shortened. The ring main unit adapter comprises a universal interface and a variable interface. The universal interface and the variable interface are connected through a connecting plate. The universal interface comprises an insulating layer 1, and a conducting tube 1 arranged in the insulating layer 1. A through hole is formed in the middle of the connecting plate. The variable interface comprises an insulating layer 2 and a conducting tube 2 arranged in the insulating layer 2 and formed by two arc-shaped copper sheets. According to the invention, the adapter is connected between the twoT-shaped joints or between a T-shaped joint and a substrate, and then the connection/disconnection of T-shaped joints, and the T-shaped joint and the substrate can be conveniently realized. The working time is saved. The two ends of the adapter are provided with the universal interface and the variable interface. The universal interface is connected with a standard component, and the variable interface is connected with another component. In this way, the tight connection can be realized through adjusting the spacing between the two copper sheets of the conducting tube of the variable interface, in regardless of the diameter size of the conducting tube to which the variable interface is connected. As a result, the reliable electrical conductivity is achieved.