Abstract: The pyrolysis of Shengli lignite (5-8 mm) under CO₂ atmosphere was investigated at the temperature from 400 to 700℃ in a fixed bed reactor, the effect of CO₂ on the distribution of gas, solid and liquid phase in the product was analyzed, and the influence mechanism on the char structure under CO₂ atmosphere was explored. The results indicate that the yields of tar and water from pyrolysis under CO₂ atmosphere are higher than that under N₂ atmosphere, with a decrease in char and gas yield. At 400℃ and 500℃, the surface area and pore volume of the char prepared under CO₂ atmosphere are nearly the same as that under N₂ atmosphere, while at 600 and 700℃, the surface area and pore volume of the char prepared under CO₂ atmosphere are higher than that under N₂ atmosphere. It maybe attributes to that CO₂ can not only promote the release of volatile, but can also react with the active sites in the channels of char. The introduction of CO₂ into pyrolysis can increase the aromaticity of char due to the consumption of 3-5 rings aromatic structures. The yields of H₂ and CH₄ obtained from pyrolysis under CO₂ atmosphere are lower than that obtained under N₂ atmosphere at 600 and 700℃, and the yield of CO is much higher because of the occurrence of the char-CO₂ reaction.