A transformer iron core ground detector comprises a copper pipe group (1), a clamping plate (2), a fixing box (4) and a feed-through current transducer (7). One end of the copper pipe group (1) is connected with a transformer iron core while the other end of the copper pipe group (1) is connected to the ground on the lower portion of an outer casing of a transformer oil tank, the copper pipe group (1) penetrates through the feed-through current transducer (7), the feed-through current transducer (7) is provided with an end connector (5) and a plastic coated hose (6), the fixing box (4) is provided with a through hole, the feed-through current transducer (7) is arranged in the fixing box (4), the end connector (5) of the feed-through current transducer (7) is arranged in the through hole of the fixing box (4), the plastic coated hose (6) connected with the end connector (5) is arranged at the outer end of the end connector (5) of the feed-through current transducer (7), and the clamping plate (2) and the fixing box (4) are clamped on two sides of the copper pipe group (1) and connected to each other detachably so that the transformer iron core ground detector is more convenient in installation.