Bio-oil has attracted considerable interest as a promising renewable energy resource because it can be utilized as a feedstock in integrated bio-refineries for the production of highly valuable chemicals and next-generation hydrocarbon fuels. However, it is necessary to improve the bio-oil quality before it can be fed to bio-refineries. Currently, catalytic vapor cracking seems a more attractive process than catalytic upgrading technologies, such as hydrotreating and esterification, in order to improve the bio-oil quality. This review presents a summary of recent research and the state of art technology for the catalytic vapor cracking of bio-oil, focusing on the catalysts applied, upgrading methods and reaction mechanisms.