The invention provides an anticorrosion protection device for a floating-roof petroleum storage tank, belongs to the technical field of the petrochemical industry, and solves problems that petroleum tanks are poor in anticorrosion capability and unsafe in the prior art. The floating-roof petroleum storage tank comprises a tank bod and a floating cover; the anticorrosion protection device comprises an elastic spiral body made of an insulating material; the elastic spiral body is supported between the bottom of the tank body and the floating cover and is provided with a plurality of sacrificial anode material blocks sequentially from top to bottom; the sacrificial anode material blocks are connected with the floating cover by the aid of leads; and the floating cover is connected with the tank body by the aid of a lead. The device has the advantages of being safe, reliable, convenient to mount and maintain and the like.