Abstract: Since 1993, Shanghai Urban Rail Transit has been in operation for nearly 28 years, and some old lines have been unable to meet the need of Shanghai's high density, high reliability and high performance super large-scale network operation. Therefore, the problems of backward signaling system, aging equipment and weak technical support need to be solved through signaling system transformation to improve the operation service quality. Taking the signaling system transformation of Shanghai Metro Line 3/4 as an example, from the perspective of multiple dimensions including demand, construction period, impact and benefit, the preliminary analysis and scheme comparison of the signaling system transformation project is studied. Finally, it is recommended to adopt CBTC train control system as the transformation scheme for Shanghai Metro Line 3/4.