Abstract: The process of bio-oil pyrolysis/gasification and gas evolution characteristic was studied using a thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR). Pyrolysis/gasification of bio-oil and its fractions were also performed in a fixed bed. As a result, the process of bio-oil pyrolysis/gasification can be divided into two stages. The first is volatilization and pyrolysis of the light compounds at low temperature and the second is cracking and polymerization of the heavy compounds at high temperature. The values of activation energy are 35~38 kJ/mol in the first stage and 15~22 kJ/mol in the second stage, respectively. With temperature increasing, the conversation of pyrolysis/gasification grows higher and the yield of synthesis gas (syngas) increases. However, the calorific value of the gas has an inverse correlation with the temperature. In comparison, the light fraction (LF) makes more contribution to the overall H₂ release; while CO and CH₄ are mainly generated from the heavy fraction (HF).