The invention belongs to the technical field of offshore wind power foundation, and discloses a novel offshore wind power submersible floating foundation and a construction method thereof. The foundation consists of a floating platform and a mooring system. The floating platform comprises a standing column, a floating box and an inclined supporting rod. The mooring system comprises a straight mooring line, an inclined mooring line and a plurality of anchoring units connected through beam elements. During construction, the floating platform and the mooring system with upper draught fan tower barrels are towed separately, and the anchoring units sink and are embedded in the seabed; the upper ends of the straight mooring line and the inclined mooring line pass through reserved hole channels and the inclined supporting rod, and anchoring is conducted on the inclined mooring line and the straight mooring line after the floating platform sinks to the position. The foundation provides enoughbuoyancy stability when towing is conducted, is less affected by wave load when in position, achieves a water tension system, and reduces the difficulty of installing mooring line under water, anchoring foundation provides anti-pulling force through ballast load and friction resistance, the foundation penetrates the seabed through surcharge and internal and external pressure difference, and construction is convenient.