The invention relates to an encircling marine organism clearing robot used for the outer surface of an undersea steel structure pipeline. The robot comprises a robot traveling unit and a movable clearing unit arranged on the robot traveling unit. The robot traveling unit comprises an upper arc-shaped fixing plate, a lower arc-shaped fixing plate, a magnetic suspension adsorption assembly, a travelling drive mechanism and a lifting mechanism, wherein the upper arc-shaped fixing plate and the lower arc-shaped fixing plate are arranged parallel to each other; and the magnetic suspension adsorption assembly, the travelling drive mechanism and the lifting mechanism are arranged between the upper arc-shaped fixing plate and the lower arc-shaped fixing plate. The movable clearing unit comprises an arc-shaped fixing support arranged on the upper arc-shaped fixing plate, an arc-shaped rack arranged on the arc-shaped fixing support, and a cavitation water jet mechanism which is movably arranged on the arc-shaped fixing support in the circumferential direction and is engaged with the arc-shaped rack. Compared with the prior art, the cavitation water jet mode is adopted for clearing marine organisms on the outer surface of the undersea steel structure pipeline, so that the clearing efficiency is high, clearing cost is low, working is stable, dismounting and mounting are convenient, safety is good, and the applied range is wide.