The invention discloses an anti-corrosion device for a water side system of a sleeve heat exchanger and an anti-corrosion treatment method for the water side system of the sleeve heat exchanger. The sleeve heat exchanger comprises a water inlet pipe and a water outlet pipe, the anti-corrosion device is arranged at the end part of the water inlet pipe and the end part of the water outlet pipe, andcomprises a shielding and blocking structure, wherein the shielding and blocking structure comprises a first shielding and blocking structure used for shielding and blocking a water inlet of the waterinlet pipe and a second shielding and blocking structure used for shielding and blocking a water outlet of the water outlet pipe. According to the anti-corrosion device, the first shielding and blocking structure and the second shielding and blocking structure are arranged to enable the water side system of the sleeve heat exchanger to form a sealing structure, so that large pressure can be borne, and the anti-corrosion protection is carried out by filling the sealing structure with the protective gas, so that corrosion from ant nests of the water side system can be effectively prevented.