This work studies the NH3 plasma passivation on a novel gate-all-around poly-Si TFTs with multiple nanowire channels (GAA-MNC TFTs). The NH3 plasma passivation can effectively passivate the defects in poly-Si channel and improve the electrical performance of poly-Si TFTs. As comparison to conventional TFTs, the GAA-MNC TFTs with NH3 plasma passivation exhibit outstanding three-dimensional gate controllability and excellent electrical characteristics, which revealed a high ON/OFF current ratio (>108), a low threshold voltage, a steep subthreshold swing, and a near-free drain-induced barrier lowering. Therefore, such the high-performance GAA-MNC TFTs are very suitable for the applications in the system-on-panel (SOP) and three-dimensional (3D) circuits.