The invention discloses an ocean platform crane. The ocean platform crane comprises a lower cylinder, a bearing assembly, an upper cylinder, a rotary table, a propeller strut, a pulley set, a steel rope, a cantilever crane, a winch and a rotary motor. The ocean platform crane adopts three rows of ball type slewing bearings as the bearing assembly, the bearing capacities of rolling bodies are definite through the three rows of ball type slewing bearings, the bearing performance of all bearing pin rollers is given full play, relatively large axial force, radial force and bearing capacity of capsizing moment are achieved, and the requirement on the slewing bearings of the large ocean platform crane is met.