The cellulose pyrolysis processes under the individual and synergistic effects of CaO and K2HPO4 center dot 3H(2)O were studied by the thermogravimetric-mass spectrometric analysis (TG-MS) technique, mainly focusing on the changes of some important products such as CH4 during the pyrolysis process under different conditions. The experimental results showed that after the addition of CaO, the amounts of CO, CH4, and other species decreased. CaO could fix the "CO2-like reactive intermediate" produced during the cellulose pyrolysis process, thus reducing the evolution of CO2 in the temperature range of 300-440 degrees C and continuing the CO2 evolution in the temperature range of 520-710 degrees C. When K2HPO4 center dot 3H(2)O was added, the amounts of CO, CH4, CO2, and other gaseous species increased, indicating that K2HPO4 center dot 3H(2)O could significantly change the pyrolysis reaction process, such as promoting the benzene ring formation reactions involving small molecules such as toluene. When the mixture of CaO and K2HPO4 center dot 3H(2)O was added, the weight loss at the initial stage of pyrolysis was relatively moderate compared to that adding K2HPO4 center dot 3H(2)O alone. At the same time, an obvious weight loss appears in the pyrolysis process in the temperature range of 600-770 degrees C, and the amounts of various species generated increased compared to those generated in the single catalytic pyrolysis. Therefore, CaO and K2HPO4 center dot 3H(2)O exhibited a strong synergistic effect in the pyrolysis process.