The invention discloses a subway tunnel leakage monitoring and early warning system and a method. The system comprises a parallel electrical acquisition subsystem, a wifi gateway and a data monitoring subsystem. The parallel electrical acquisition subsystem is used for realizing acquisition of electrical data in a tunnel. An electrical big line is arranged on the side wall of the tunnel and is electrically connected with a parallel electrical prospecting apparatus host. An electrode is connected to the electrical big line through a plug-pull clip. An infinity B pole and a public comparison electrode N pole are electrically connected with the parallel electrical prospecting apparatus host. The parallel electrical prospecting apparatus host is fixedly installed on one side of the inner side of the tunnel and is powered by a power supply conversion device. The wifi gateway is used for achieving network linkage and instant messaging of the data monitoring subsystem and the parallel electrical acquisition subsystem. The data monitoring subsystem is used for storing, managing and intelligently processing and analyzing the electrical data, and achieving remote control on the parallel electrical acquisition subsystem and dynamic monitoring and active early warning for tunnel leakage water damages.