Experiments on carbon monoxide generation principle of pine which has been widely used in the historical buildings in Tibet were conducted in a combustion cabin in high-altitude-region Lhasa and low-altitude-region Hefei respectively. Three pine samples with different sizes were adopted. The surface temperature and CO concentration under radiative heat flux of 42 kW/m2 were measured. The effect of oxygen quantity and pressure on carbon monoxide production were analyzed. It was found from the experimental results that carbon monoxide generation had the same trend in both districts; it was first steadily released to a peak value, subsequently descended to a constant value, and then increased to a second value and decayed in the end. Comparing with those in Hefei, the two peak values and the steady value of carbon monoxide concentration in Lhasa were higher, and also, the time to them was much later. The main reason is that the quicker increasing temperature in lower-oxygen condition in Lhasa accelerated the incomplete oxidation of unburned hydrocarbons. Additionally, low mixing rate of volatile component and oxygen under the condition of low oxygen quantity and the ambient pressure was in favor of incomplete combustion of pine and therefore carbon monoxide production.