The invention discloses a drilling platform self-leveling device and a construction method thereof, and relates to the field of bridge construction. The drilling platform self-leveling device comprises a casing pipe, a supporting pile, a distributive girder and a connecting part, wherein the supporting pile can reciprocate in the casing pipe, a support is fixed to the outer wall of the casing pipe, a template beam is fixed to the outer wall of the supporting pile and located between the support and the distributive girder, and the support, the template beam and the distributive girder are all detachably connected with the connecting part. The drilling platform self-leveling device further comprises an adjusting mechanism with one end fixed to the supporting pile and the other end fixed to the distributive girder, and the adjusting mechanism can stretch and retract between the supporting pile and the distributive girder. The drilling platform self-leveling device is convenient to mount and capable of improving construction efficiency, and a smooth drilling platform can be established on the sea surface without reference targets.