The invention provides a treatment device of cold rolling phosphorus-containing wastewater, which comprises a positive electrode chamber, a negative electrode chamber and a primary cell internal circuit which is used for separating the positive electrode chamber and negative electrode chamber and composed of separation membranes, wherein an inert electrode used as the positive electrode is arranged in the positive electrode chamber; an iron-carbon alloy micronet separation component, which is used as a negative electrode and has the action of physical entrapment, is arranged in the negative electrode chamber; the inert electrode and iron-carbon alloy micronet separation component are connected with through an external circuit; the external circuit and internal circuit are connected to constitute a complete primary cell; the upper part of the negative electrode chamber is provided with a water inlet pipe; the iron-carbon alloy micronet separation component is connected with a water outlet pipe; and the lower sides of the positive electrode chamber and negative electrode chamber are respectively provided with a sludge discharge pipe and a sludge discharge pipe. The treatment device can effectively convert phosphorus in the cold rolling wastewater into a phosphate precipitate in a primary cell-chemical flocculation coupled mode, thereby separating out the phosphorus. The method can effectively remove phosphorus and organic matters, and can obtain favorable effluent water quality and recover electric power through the iron-carbon alloy micronet.