A preparation method of a polyatom doped carbon/polyaniline composite material for a supercapacitor belonging to the technical field of carbon materials and supercapacitors. The method comprises the following steps: pretreating a material, activating and carbonizing at a high temperature, physically absorbing organic pollutants and compounding through polyaniline electrodeposition. The invention effectively utilizes a biomass resource to prepare a biomass carbon material. The biomass carbon is modified by absorbing the organic pollutants in wastewater, so the problem of wastewater pollution issolved, simultaneously the wasting problem of resources is solved by utilizing pollutants, and a novel electrode material is also obtained. The final material has a good capacitance performance. In the 1M H<2>SO<4> electrolyte, the current density is 0.1A/g; the maximum specific capacitance can reach 557F/g; the rate performance is excellent; simultaneously the energy density is high which is upto 30.33Wh/kg.