The invention provides an air-conditioning system with a large diving depth deepwater platform. The air-conditioning system comprises an air-handling unit composed of an air return section, an air filter, a forced draught blower, a cooling coil, a water stopping plate and an air feeding section which are sequentially arranged in the air inlet direction; refrigerating fluid in a refrigeration compressor is controlled through a pipe to be conveyed to two condenser for condensation, the refrigerating fluid obtained after condensation is controlled through a pipe to flow to an expansion valve and then be conveyed to the cooling coil for absorbing heat, the refrigerating fluid obtained after heat absorbing flows into the refrigeration compressor for circulation, one condenser is provided with a cooling water supply and discharge pipe communicated with external seawater, and the other condenser comprises a plurality of heat exchange pipes arranged on the inner wall faces of a pressure-resisting cabin of the deepwater platform in parallel; the cross sections of the heat exchange pipes are in semi-closed shapes with openings, opening sides of the cross sections of the heat exchange pipes are attached to the inner wall face of the pressure-resisting cabin to form a refrigerating fluid closed flowing space, and the outer wall face of the peripheral wall, exposed out of the pressure-resisting cabin, of the closed flowing space is wrapped with a heat insulating layer.