Abstract: Objective: Shanghai Rail Transit Line 1 (hereinafter referred to as ′Line 1′) has been in operation for more than 20 years, and the signaling equipment is aging severely. The system stability needs to be improved through equipment overhaul and renovation. However, the night construction time is tight, and the risk of signaling system debugging and switchover is relatively high, which should not affect the normal operation of the next day as well. It is necessary to find a suitable signaling system switchover scheme. Method: By carefully analyzing the construction and debugging steps, taking into consideration that the original system is still used after the overhaul of Line 1, a lot of equipment are shared for daytime operation and nighttime testing, requiring a large number of switchover switches. The conventional switchover switch needs a long operation time, multiple operation steps, having many uncertain factors and high risks during switchover connection. At the same time, it also requires a fully switchover operation to the original system after each construction. Under various limited conditions, the switchover scheme between the new and old systems has become a crucial link to ensure safety. After analysis, and argumentation, scheme comparison and onsite testing, it is was ultimately decided to replace the conventional switches with relays. Result & Conclusion: Using relay nodes to form circuits for switching between different systems can save an additional 25 minutes of night construction time, and no switchover errors occur throughout the entire debugging construction. This scheme is more suitable for signaling system overhaul projects such as Line 1, which has short nighttime debugging construction time, a lot of switchover equipment, and high safety requirements.