Bio-oil from fast biomass pyrolysis has poor fuel properties due to the presence of substantial amounts of water, carboxylic acids, phenolic derivatives, anhydrosugars and other hydroxyl-containing compounds.It must be upgraded to be more combustible, more stable during transport and storage, and to have a higher heating value and lower acidity before engine fuel applications can be realized.Hydrodeoxygenation (HDO) has been tried in the past but large amounts of hydrogen must be consumed to go from 35-50% O to < 1% O to make contemporary type of fuel.Furthermore, catalyst coking and low catalyst lifetimes have further prevented a satisfactory progress development.Catalytic upgrading bio-oil by additions across olefins over solid acids can be carried out at lower temperatures (80-150 ℃) and autogenous pressures.Through this approach, bio-oil can be partially refined to combustible and stable oxygen-containing organic fuels and all the original oxygen and all the fuel value in the original bio-oil were maintained.In this study, recent progresses of bio-oil upgrading with olefins were mainly reviewed.Also, the main problems and future trends of bio-oil upgrading through olefin additions were presented.