[Objective] At present, the signal equipment in stations of Shanghai Metro Line 7 enters the aging cycle, which directly affects the stability and reliability of the power supply system of Line 7. It is necessary to upgrade the signal equipment on the premise of ensuring that the function of the centralized signal control equipment in the main substation remains the same. [Method] With Shanghai Metro Line 7 as the research object, the function of the centralized signal control equipment in the main substation is introduced. On the premise that the original functions are not affected, the transformation principle of hardware platform consistency and software functionality consistency is proposed. The hardware transformation of the equipment is introduced mainly from the aspects of centralized signal cabinet, protection and measurement device in 110 kV main substation, and serial port signal of comprehensive protection equipment. The new engineer workstation based on Unix system is introduced. The centralized signal control equipment in the main substation is debugged and its functions are verified. [Result & Conclusion] The debugging results and function verification show that the new centralized signal control equipment is functionally compatible with the existing equipment, the signal delay and false alarm caused by the aging of the original equipment are eliminated, and the transformation requirements are met.