The invention discloses an underwater acoustics and pressure combined ship detection device and a detection method thereof. The existing methods of ship detection mainly include video surveillance, active acoustic detection, passive acoustic detection, and AIS automatic identification system and synthetic aperture radar remote sensing detection. The underwater acoustics and pressure combined ship detection device comprises an integrated control unit and m detection devices. Each node information processing unit comprises a hydrophone, a second AD conversion module, a sound signal processing module, a first storage module, a first decoding module, a second encoding module, a second communication module, a pressure signal processing module, an equipment self-check module, a wave power generation module, a second battery, and a second power control module. Underwater sound is detected preliminarily through the hydrophones. When an abnormal signal is found, pressure sensors are activated to detect the surface wave and identify ship wave from the surface wave. The energy consumption for detection is reduced, and the service time is increased.