The invention relates to a sacrificial anode protection device, in particular to a replaceable sacrificial anode well used for protecting underground pipelines and a replacement method of the replaceable sacrificial anode well. The purpose of the invention is to provide the replaceable sacrificial anode well and the replacement method thereof, and the replaceable sacrificial anode well is simple in structure, saves time and labor, and is low in cost, simple and convenient to operate, low in excavation difficulty and long in service life. The replaceable sacrificial anode well comprises a well body (1), fillers (2), two sacrificial anodes (3) and an insulation board (4), wherein the well body (1) is communicated with a pipeline; the insulation board (4) is axially arranged in the well body (1) and used for dividing the interior of the well body into two cavities; each cavity is filled with the fillers (2); a sacrificial anode (3) is arranged at each of the upper parts in the cavities; each sacrificial anode (3) is connected with the pipeline through a lead wire.