Abstract: In the renewal and transformation of urban rail transit existing signaling system, it is necessary to design a special reverse connection device to realize the safe and fast reverse cutting of the equipment/interface shared by the new and old systems. Taking the implementation of signaling system renewal and transformation project of Guangzhou Metro Line 1 as background, the reverse connection scheme and implementation steps of the switch machine in the new and old systems are expounded by analyzing the design principle, type selection and working principle of the reverse connection device, providing reference for other similar projects in China.