Abstract: TG-MS was used to analyze the cellulose pyrolysis process under individual and synergistic action of CaO and K₂HPO₄.3H₂O, focusing on the changes of products such as H₂, CH₄ under different conditions during the pyrolysis. The results show that after CaO is added, the amount of H₂, CO increases, and the amount of CH₄,CO₂ and other gases decreases during cellulose pyrolysis. CaO can fix acid products and precursors produced during cellulose pyrolysis, thus reduce the amount of CO₂ precipitation of region 271-465℃, and keep CO₂ precipitation of region 560-721℃. After K₂HPO₄·3H₂O is added, the amount of H₂, CO is reduced, and the amount of CH₄, CO₂ is increased, and K₂HPO₄·3H₂O can significantly change process of pyrolysis reaction, such as promoting the benzene ring formation reactions. After the mixture of CaO and K₂HPO₄·3H₂O is added, the weight loss process at the beginning of pyrolysis is more moderate than that of K₂HPO₄·3H₂O alone, and the amount of most gases is increased. CaO and K₂HPO₄·3H₂O has strong synergistic effects in the pyrolysis process.