The utility model relates to an anti-theft device for an oil measuring hole of an overhead tank. The anti-theft device comprises an anti-theft key and an anti-theft body capable of being fixedly connected to an oil gauging hole of the elevated tank. A through polygonal through hole is formed in the anti-theft body; an anti-theft sliding block which is taken out by an anti-theft key is arranged inthe polygonal through hole in a supporting manner; the anti-theft sliding block is provided with a through sliding block through hole, a protection block capable of blocking the polygonal through holeis arranged in the polygonal through hole and located below the anti-theft sliding block, an ejector pin penetrates through the protection block and the anti-theft sliding block in a sliding mode, and the top end of the ejector pin protrudes out of the top face of the anti-theft sliding block. And an anti-theft cover disassembled by the anti-theft key is concavely arranged at the top of the anti-theft body. The anti-theft device for the oil gauging hole of the elevated tank overcomes the problem of poor anti-theft effect of the oil gauging hole of the elevated tank in the prior art, is mounted on the oil gauging hole of the elevated tank, is convenient to open and close, is high in safety, and can effectively prevent oil from being stolen.