Two-dimensional porous carbon materials are very promising for energy storage/conversion due to their unique microstructure, reasonable pore structure and excellent electrochemical properties. A green and facile in-situ carbonization technique is innovated to prepare a unique porous lignin-derived carbon quasi-nanosheets (PLC) with rational pore distribution, large surface area, and excellent conductivity. The lignosulfonate/zinc oxalate composite was firstly self-assembled by hydrophobic bond of the amphiphilic structure in lignosulfonate using ethanol/water solvent without the need to use any toxic material, followed by co-pyrolysis at a high temperature with gas-exfoliation and in-situ templating of zinc oxalate. The resulting PLC exhibits a very high specific capacitance of 320 F/g at 1.0 A/g and long cycling stability (remains 93.5% after 10,000 cycles at 5.0 A/g). In addition, when assembling into symmetric supercapacitors in PVA/KOH gel electrolytes, PLC also shows a high specific capacitance of 274 F/g at 0.5 A/g with excellent rate capability and a high specific energy density (9.75 W h/kg at 6157.9 W/kg). These excellent electrochemical performances indicate that the as-prepared PLC should hold great promise for the energy storage devices, opening a new path for the preparation of advanced carbon electrode material and high-value-added utilization of biomass.