This work demonstrated a facile one-pot in-situ method to prepare lignin-based carbon/ZnO (LC/ZnO) nanocomposites by using lignin that was extracted from paper pulping waste liquor as the carbon source. The morphological, physical and optical properties of the prepared LC/ZnO nanocomposites was characterized with Scanning electron microscope (SEM), Transmission electron microscopy (TEM), Thermal-gravimetric analysis (TGA), Raman, X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses. The resulting LC/ZnO is composed of highly dispersed ZnO nanoparticles embedded on a lignin-based carbon nanosheet. The typical D and G bonds of carbon materials obviously appeared. The TGA shows that the LC contents could be controlled. The BET surface area of the LC/ZnO was much larger than the BET surface area of the pure ZnO. The prepared LC/ZnO nanocomposites exhibited excellent photo catalytic performance for the degradation of organic dyes. LC/ZnO that contained similar to 638% lignin-based carbon exhibited an excellent photo-degradation efficiency of methyl orange as high as 98.9% under sunlight irradiation for 30 min, superior to the performance of pure ZnO and other reported ZnO/GRs. The improved photocatalytic performance was attributed to a homogeneous structure and stronger absorption ability for organic dyes. The mechanism exploration experiment showed that h(+) was the main active specie. Meanwhile, the photocatalytic electron transfer mechanism was also investigated. In addition, this work demonstrates a green and valuable pathway for the high-value-added utilization of lignin. (C) 2017 Elsevier B.V. All rights reserved.