The invention provides a comprehensive platform with a floating type full concrete structure with an underwater storage tank for well drilling, well workover, production, public use and household. The platform has 12 different modes, and each mode consists of a liquid storage system, supporting legs, an upper facility and an anchoring leg positioning system. The platform not only has a series of characteristics and advantages, such as SPAR platform heavy draught, small waterplane area, higher center of buoyancy than center of gravity, platform natural period more than the wave period corresponding to once-in-a-century significant wave height and the like, has the function of liquid (oil) storage, and maintains the draught depth of the platform in the process of oil storage and discharge operation unchanged. The platform matched with a single-point or multi-point anchoring device can form a complete development system for production, well drilling, well workover, storage and outward transportation of offshore petroleum and natural gas; the platform not only can be used for development of an offshore large and deepwater oil-gas field with long production life, but also can be used for a small and deepwater oil-gas field with short production life, in particular the development of a marginal oil-gas field. After development of the oil-gas field is finished, the platform can be transferred and reused conveniently.