The invention provides a sand blasting derusting system for ships, and relates to the technical field of mechanized equipment. A wall-climbing robot subsystem capable of achieving remote control is arranged, and therefore free movement of sand blasting derusting equipment on ship bodies can be achieved, manual high-altitude operation generated when a sand blasting derusting method is used for removing rust on the ship bodies can be replaced, risks and manual cost generated in the ship derusting process are reduced, and the chip derusting efficiency can be improved; and in addition, an elastic sealing ring is arranged between a sealing cover and the ship bodies, elastic sealing between the sealing cover and the ship bodies can be achieved, in other words, it can be guaranteed that no gap exists between the sealing cover and the ship bodies in the working process, and dust generated in the sand blasting process can be effectively prevented from escaping from the sealing cover, entering air and causing environment pollution.