In our work, the porous carbon nanosheets (PCNs) are successfully prepared using one-step activation and carbonization of the naturally hollow tube-like dandelion fluffs. The dandelion fluff with hollow tube structure is composed of aligned nanocellulose, enabling the facile activating agent (KOH) permeation, which can activate the dandelion fluff into porous interconnected carbon nanosheets. The obtained porous interconnected graphene-like structure of the activated carbon material contributes to the electrolyte permeation and electron transfer, which is beneficial to enhance the electrochemical performances, especially the rate capability. Manganese dioxide (MnO2) modified PCNs composited with MnO2 is prepared as the positive electrode for asymmetric supercapacitor using in-situ microwave deposition method. The conformally coated MnO2 on PCNs can facilitate the ion diffusion and the electron transport, which contribute to the enhancement of the rate performance. Herein, the assembly asymmetric supercapacitor based on PCNs and MnO2/PCNs composite displays an energy density as high as 28.2 Wh kg(-1) at the power density of 899.36 W kg(-1) and a good capacitance retention of 89% after 10,000 cycles. These results present that the graphene-like cross-linked carbon material is a promising electrode material for high-efficiency electrochemical energy storage and conversion.