Abstract: The paper summarized current studies concerning phododegradation of lignin model and natural lignin. The results of lignin model studies showed that lignin photodegradation was a typical free radical reaction, and hydroxyl radical, carbonyl groups and phenacyl aryl ether cleavage were the main type of reaction. Moreover, phenoxy radical was very important intermediate product. Lignin photodegradation is an oxidation and degradation process, during which carbon′s oxidation state raised, conjugated carbonyl increased and nonconjugated carbonyl decreased, followed by high molecular lignin depolomerizing to some extent, α-quinone and β-quinone were main reason contribute to the discolor, there were soluble small molecular product such as benzoic acid and benzaldehyde. In the end, the paper pointed out the key problem of the current study and the development direction.