The invention discloses a deep water pipeline multi-circuit bridging system and a testing and installing method thereof. The deep water pipeline multi-circuit bridging system comprises a seabed manifold, an underwater electric distribution assembly, a first underwater Christmas tree, a second underwater Christmas tree, a first underwater umbilical cable terminal and a second underwater umbilical cable terminal, wherein the seabed manifold, the underwater electric distribution assembly, the first underwater Christmas tree, the second underwater Christmas tree, the first underwater umbilical cable terminal and the second underwater umbilical cable terminal are connected through a hydraulic bridging wire and a water and gas injection pipeline. The hydraulic bridging wire comprises male connector terminals and female connector terminals matched with the male connector terminals. The testing and installing method of the deep water pipeline multi-circuit bridging system includes the following steps that a leakage test and a flushing test are performed on the male connector terminals and the female connector terminals, after the tests are finished, the water and gas injection pipeline and the hydraulic bridging wire are moved underwater, and the water and gas injection pipeline and the hydraulic bridging wire are installed between underwater equipment respectively through the ROV operation. According to the deep water pipeline multi-circuit bridging system and the testing and installing method thereof, fast connecting and disconnecting between the underwater equipment can be achieved, it is ensured that all key parts and moving portions can be recycled, and the stopping and connecting states of an ROV can be safe and reliable.