Photocatalytic degradation of lignin and the degradation of macromolecular lignin into small molecule value-added products are efficient and environmental protection method. Firstly, the mechanism of photocatalytic degradation of lignin was reviewed, including the formation path of photogenerated holes ("h" _"VB" ^"+" ) / electrons ("e" _"CB" ^"-" ), ·OH and O2-· and their respective action mechanisms on β-O-4 bond breakage. Secondly, the influence on photocatalytic degradation of lignin includes reaction pH, type, improvement and dosage of photocatalyst, type and dosage of oxidant, and the combination between photocatalyst and oxidant was summarized. Finally, the photocatalytic degradation of lignin was prospected.