The invention discloses a construction method of an offshore elevated platform, which comprises the steps: A. a plurality of groups of first bases are welded around the elevated platform, wherein each group comprises three continuously arranged first bases; B. a second base is fixedly connected to the first base in the middle of each group, another two first bases are fixedly connected with guiding support legs, the top ends of the guiding support legs are fixedly connected with base clamps, and the guiding support legs are further fixed through support leg gland structures; C. the support legs of the elevated platform are respectively inserted into the sea floor along the two base clamps and the arc parts of the second bases, and the support legs of the elevated platform are respectivelyfixed through guiding pressing plates; D. pier bases are inserted into the sea floor by sections in sequence in the middle area surrounded by the three legs of the elevated platform; and E. a drilling machine is fixed on the elevated platform and used for drilling the seafloor rock mass and the sea sludge layer at the bottom end of the pier bases through, then the impurities are pumped out through a sludge pump, and finally reinforcing steel bars are arranged into the pier bases, and the concrete is cast.