The invention relates to a crane ship and a hoisting operation method, and belongs to the technical field of ships. The crane ship comprises a semi-submersible main ship body and a plurality of cargobooms detachably mounted on the main ship body, a ballast tank is arranged in the main ship body, and a telescopic full-revolving propeller is mounted at the bottom of the bow of the main ship body. Afull-revolving propeller is mounted at the bottom of the stern of the main ship body, each hoisting arm comprises a hoisting beam and a bearing piece arranged at the end part of the hoisting beam, and the hoisting beam can transversely move along the main ship body. The end part of the hoisting beam transversely extends out of the main ship body during hoisting operation, and the bearing piece can vertically rise and fall relative to the hoisting beam through hydraulic drive. The crane ship can be dynamically positioned in an operation area, the bearing piece extends out to an operation position through the transverse extending of the hoisting beam, and the bearing piece is hydraulically driven to vertically rise and fall to be matched with the ballast adjustment, so that the hoisting operation can be quickly completed. The crane ship can work separately and can also work together with other crane ships. The operation method is flexible and high in operation efficiency.