The invention discloses a device and a method for adding zinc to ADS reactor lead-bismuth eutectic alloy. The device comprises an ADS reactor with a zinc adding tube, wherein a zinc adding tube 1 passing through a zinc adding hole is arranged in the ADS reactor, the zinc adding tube 1 extends to be close to a reactor core of the reactor, a closeable sealing cover is arranged in the zinc adding hole, a containing part and a spraying part are arranged outside the sealing cover, so that zinc powder or weak acid zinc salt or an additive containing zinc element can be conveniently added to the reactor core through the zinc adding hole, so that a cooling agent in the reactor core contains the zinc element, and by controlling the addition of the zinc element, a layer of dense oxide thin film is formed inside the reactor core, so that the service life of the reactor is prolonged, and the safety of the reactor is improved.