This series arc furnace hydrocooling composite conducting arm are of rectangular frame structure,welded of copper-steelcomposite plate,the upper layer of copper plate conducts current,so it’s the conduction function of the electrode arm and electrode supporing function integrated in one device.Due to the abandon of traditional conducting copper pipe on the electrode arm and eliminating of many insulating parts,the structure is simplified with larger conducting surface,substantial contact resistance reductiong is achieved and it also means low maintenance work.It is extensively applicable to arc furance with capacities of 5T to 100T,and large steel ladle refining furance.