The invention relates to a preparation method of a 
biomass carbon-based 
electrode for an asymmetric 
capacitance desalting device, which comprises the following steps: cleaning 
shrimp and crab shells,carrying out ultrasonic treatment, 
drying, pulverizing into 
powder, carbonizing in an 
inert atmosphere, adding an activator into a carbonized product, heating to 800-1200 DEG C under the protection ofinert gas, keeping the temperature for 2-4 hours, cooling, 
pickling, washing with water, filtering, and 
drying to obtain 
nitrogen-doped 
porous carbon; respectively carrying out 
sulfide modification and positive charge modification on the 
nitrogen-doped 
porous carbon, dispersing the modified 
nitrogen-doped 
porous carbon, 
acetylene black and 
polytetrafluoroethylene in absolute ethyl 
alcohol, evaporating to a paste, 
coating conductive substrate 
graphite paper with the paste, 
drying, and assembling to form an asymmetric 
electrode, wherein the positive 
electrode is positive charge modified nitrogen-doped porous carbon, and the negative electrode is 
sulfide-modified nitrogen-doped porous carbon. According to the method, the 
shrimp and crab shells are used as precursors, a 
nitrogen source does not need to be additionally added, raw materials are easy to obtain, cost is low, large-scale production can be achieved, and the prepared electrode is large in adsorption capacity and high in efficiency.