Abstract: The differences in the composition of the oxygenated compounds in bio-oil prepared by different biomass were presented. Then the reaction mechanisms of hydrodeoxygenation(HDO) of the main oxygenated compounds(phenols,furans,ethers,acids and esters) were reviewed,and the HDO kinetic data and reaction pathways were described in detail. Meanwhile,the HDO reaction processes of real bio-oil feeds were sketched,and the removal activities of heteroatoms O,N,S catalyzed by different catalysts were also discussed. Moreover,the problem of the hydrotreating of bio-oil was pointed out that we know little about the reaction mechanism of real bio-oil,and the HDO of model compounds can not reflect the reaction process of real bio-oil,thus the interaction of different types of oxygenated compounds and the reaction mechanism of real bio-oil should emphasically be studied.