A wind energy, wave energy and tidal energy integrated power generation system based on monopile foundation, in which the wind energy, wave energy and tidal energy will share the support structure and power transmission system, belongs to the technical field of ocean renewable energy utilization. An integrated power generation system which integrates wind energy converter, oscillating water column wave energy converter and horizontal-axis tidal energy converter is established based on the monopile support structure. The invention makes sufficient use of offshore renewable resources, so as to improve the utilization ratio of monopile foundation and reduce the total cost of power generation of integrated system. The novel integrated power generation system improves the effective utilization of the ocean areas, reduces the cost of construction and maintenance, makes full use of the existing mature wind energy technology, and promotes the commercialization of wave energy converters and tidal energy devices.