Renewable energy sources have received wide spread attention due to the limited amount of fossil fuels. Among them, forestry biomass is recognized as one of the promising candidates. In this study, we selected oak-tree as a sample forestry biomass and investigated pyrolysis characteristics of oak-tree by thermogravimetric analysis. Kinetic parameters such as activation energy and pre-exponential factor were calculated by a differential method. The average activation energy was 246.12kJ mol-1 at the conversion of 0.10-0.95.