Lignin decomposition is a dispensable process in utilizing the carbohydrates in biomass and in converting the lignin into chemicals.The decomposition and mechanism of lignin model compounds were studied in subcritical water with a batch-type subcritical biomass conversion reactor.P-hydroxy-cinnamic acid(PCA),ferulic acid(FA)were used as monomer lignin model compounds in lignin.Guaiacylglycerol-b-guaiacyl ether(GG)was selected as a representative of dimeric model compounds in lignin.In addition,the H-type(HP)and G-type(GP)β-O-4 polymer were also applied to imitate lignin.As a result,p-hydroxycinnamic acid,ferulic acid and β-O-4 lignin model compounds could be completely depolymerized.Decarboxylation reaction,cleavage of β-O-4 bonds and dealcoholized reaction were the major decomposition patterns,which were significant processes of lignin decomposition.