It is disclosed purifies industrial lignin, performs Mannich reaction on purified industrial lignin, aldehyde and amino acid, simultaneously dopes nitrogen and sulfur elements into lignin, and performs high-temperature activation to obtain the carbonized amino acid modified lignin in accordance with a principle of green chemistry; a porous carbon material is prepared from the carbonized amino acid modified lignin by means of a two-step activation method, and an electrochemical workstation is applied to investigate electrochemical performance of the carbonized amino acid modified lignin as a supercapacitor; layered porous carbon having high specific surface area is prepared, the layered porous carbon has high specific heat capacity and stable cycle performance without attenuation when the supercapacitor is prepared from the layered porous carbon, and the method used has a wide application prospect in the aspect of preparing a porous carbon material for the supercapacitor.