Lignin is one of the most abundant materials in nature, but its highly value-adding utilization is still a challenge. Herein, sodium lignosulfonate (SLS) was adopted to fabricate ZnO centering on the concept of "using lignin valuably". And the g-C3N4/S-ZnO (CNSZ) composite was successfully prepared. SLS serves as a linkage reagent, interacting with ZnO on one hand and simultaneously helping urea (processor of g-C3N4) to be deposited with ZnO. The structure and morphology of CNSZ were fully characterized. It is shown that g-C3N4 co-exists in the composite. Meanwhile, EDS and XPS analyses indicate the presence of S in the composite, which originates from SLS. The composite is found to show good photocatalytic property. Its degradation efficiency on phenol is 8.5 times higher than bare ZnO. Due to its facile synthesis and excellent property, the newly-synthesized CNSZ is anticipated to be promising for water treatment application.