Abstract: The signal system of Shanghai metro Line 2 has entered the overhaul period. Considering the technical, economic features and project feasibility, 3 types of renovation solutions for current signal system are comparatively analyzed. Combined with the operation and maintenance requirements of Line 2, the "TBTC+CBTC"(train-based and communication-based train controls) dual-signal redundant system transformation scheme is recommended, in which, the the track circuit it taken as the degraded mode of CBTC system. On this basis, the overall structure, track side structure and vehicle structure, as well as the implementation scheme of train depot and operation control center are introduced. Currently, the "TBTC+CBTC" dual-signal redundant system reconstruction scheme has been applied to train operation.