Abstract: Thermogravimetric analysis-Fourier transform infrared spectromerer（TG-FTIR） was applied to analyze the thermogravimetric and main gas products of alkali lignin pyrolysis,combined with infrared spectroscopy study of the chars from lignin pyrolysis generated different stages. The results show that the pyrolysis of lignin is divided into three phases : the moisture is volatilized below 200 ℃.Primary pyrolysis stage occurs at 200~550 ℃,the functional groups of lignin around phenyl ring broke and generated part of the gas and tar products. At 550~900 ℃,benzene or aromatic condensed into carbon. It is found that the primary gas releases from the process of lignin pyrolysis, mainly including H2 O,CO2,CO,CH4 and other hydrocarbons.CO2 product releases at lower temperature（250~450 ℃）and higher temperature section（650~750 ℃）, and an amount of CO releases at much higher temperature. In contrast, a large amount of CH4 mainly releases in the temperature range of 300~600 ℃.