The effects of addition of a high amount of CaO on the yields of pyrolysis products and the evolving of noncondensable gas from corn stalk pyrolysis at different temperatures were investigated using a fixed-bed pyrolysis system. The results showed that almost all the CO2 generated during the pyrolysis process could be absorbed by CaO (CaO/C = 1) at a lower temperature of 550-650 degrees C, and a low CO2 concentration of only 0-0.7 vol % was obtained in the noncondensable gas. The CO2 fixation into the solid phase (CaCO3) caused a big decrease in noncondensable gas yield and a significant increase in H-2 concentration. Furthermore, CaO addition could catalyze the pyrolysis process and intensify the secondary pyrolysis of volatiles to produce more H-2 and CH4. The higher heating value of noncondensable gas could achieve 19.3 MJ/m(3) at 550 degrees C. However, beyond 700 degrees C (700-850 degrees C), the CO2 absorption capability of CaO declined greatly and the CO, in the noncondensable gas increased obviously, but CaO addition could still inhibit the CO, generation compared with the trials without CaO addition. Moreover, the catalytic effect of CaO was much more significant at higher temperature in corn stalk pyrolysis. The yields of H-2 and CO increased greatly compared with those without CaO addition. The yields of CH4 and C2+ also increased and then decreased at 850 degrees C due to the thermal decomposition.