Abstract: Abstract: Bamboo is a typical agricultural and forestry biomass resource in China, which has the advantage of short growth cycle, high yield, abundant reserves. However, biomass has the disadvantages of high water content, high O/C ratio, poor grinding performance and low energy density. Torrefaction is a mild pre-pyrolysis process which operates at normal pressure, inert gas and lower temperature (200 to 300℃). Torrefaction pretreatment can effectively improve the properties of biomass, such as increasing the heating value or energy density, reducing the moisture content and O/C ratio, and improving the grinding and hydrophobicity. By these upgraded properties, the torrefaction pretreatment can also reduce the content of moisture and oxygen-containing compounds in the bio-oil, increase the heating value of bio-oil, and improve the quality and stability of bio-oil. In this paper, bamboo torrefaction was carried out in a furnace with programmed temperature controlling, Thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TGA-FTIR), pyrolyzer coupled with gas chromatography/mass spectrometer (Py-GC/MS) at different temperatures of 210, 240, 270 and 300℃. Then the effect of torrefaction temperature on the properties of the gas, solid, and liquid products was studied in order to reveal the torrefaction mechanism. The results showed that: (1) When the torrefaction temperature increased, the content of fixed carbon and C in the solid product increased significantly, resulting in an increasing of the calorific value and energy density from 18.85 MJ/kg to 23.12 MJ/kg. The oxygen content was significantly reduced, resulting in a decrease of the O/C ratio from 0.74 to 0.42. (2) Based on the FTIR analysis, the gas composition was mainly composed of H2O, CO2, CO, and CH4, and CO2 was the dominant gas, followed by H2O, CH4 and CO, and all gas content gradually increased as the torrefaction temperature increased; (3) Based on the Py-GC/MS analysis, the liquid products are mainly composed of acids, ketones, furans, phenols, aldehydes and other organic compounds. Acids, phenols and furans were the dominant components with the content of the 20.34%, 22.05% and 31.42% respectively. However, the contents of ketones and aldehydes were relatively lower, which are 10.43% and 8.26%, respectively. As the torrefaction temperature increases, the content of acid increases first and then decreases. The contents of furans, phenols, and ketones increase gradually, and the aldehyde content does not change significantly. (4) Based on the properties of gas, solid, and liquid products, the oxygen in the bamboo was mainly removed in the form of gas components (H2O, CO2 and CO, etc.) and oxygen-containing organic components (acids, phenols and furans, etc.). The torrefaction pretreatment can improve the content of C in the solid product and reduce the oxygen content, thereby increasing the energy density of bamboo. In addition, torrefaction can remove moisture and oxygen-containing compounds in bio-oil, and eventually increase the application value of biomass. This study provides basic data for the energy use of bamboo.