The invention relates to an offshore renewable energy source comprehensive power generating system, belonging to the technical field of renewable energy source power generation. The comprehensive power generating system comprises a single pile structure (1), three power generating devices and an electrical connecting circuit. The three power generating devices comprise a wind power generating device, a wave energy power generating device and a tidal energy power generating device which are respectively connected with a direct-current bus (19) in the comprehensive power generating system in parallel by three direct-drive permanent magnet generators (3-1, 3-2, 3-3) and three rectifiers (16-1, 16-2, 16-3), and connected to a reverser (21) on the bank by a seabed cable (20), and finally merged in a power grid by a boosting transformer (22). The offshore renewable energy source comprehensive power generating system can integrate the offshore wind energy power generation, wave energy power generation and tidal energy power generation to an organic combined body, and realizes the compatibility of various power generating devices and the credible connection of various power generating devices with the power grid by the electrical connecting system.