The invention relates to an oil-field water injection pipeline inner wall anticorrosion device and a replacement method. The oil-field water injection pipeline inner wall anticorrosion device at least comprises a replaceable anticorrosion device, wherein the front end and the rear end of the replaceable anticorrosion device are respectively connected with a first connection pipeline and a second connection pipeline, the other end of the first connection pipeline is connected with a water inlet connection pipeline, the other end of the second connection pipeline is connected with a water outlet connection pipeline, the water inlet connection pipeline is provided with a water inlet high-pressure ball valve, and the water outlet connection pipeline is provided with a water outlet high-pressure ball valve; and the replaceable anticorrosion device is formed by splicing two high-pressure storage pressure containers by virtue of a pressure container flange in a sealing manner, a replaceable sacrifice anode is arranged in each high-pressure storage pressure container, and one side of the top of each high-pressure storage pressure container is provided with a pressure release valve. The oil-field water injection pipeline inner wall anticorrosion device is simple in structure, simple to replace, convenient to operate when an anode in the anticorrosion device is replaced, capable of rapidly replacing the anode and capable of saving a great amount of replacement time under the situation of not influencing the operation of the anticorrosion device.