Thermochemical pretreatment of lignocellulosic biomass is a critical step in obtaining high yields of cellulose and hemicellulose-derived sugars to realize effective utilization of cellulose in renewable biofuels. The pretreatment process can quickly remove hard dissolving lignin and the physical separation of hemicelluloses in the cell wall while changing the chemical composition in plant cell wall, so as to increase the production of lignocellulose. Research with medium of sulfuric acid (H2SO4), dilute alkali (NaOH) and glycerin,and at different pretreatment temperature (117 and 135 ℃ in sulfuric acid (H2SO4)and dilute alkali (NaOH) , 117 ℃ in glycerin) analyzed and compared the main changes of chemical composition before and after the bamboo processing, and further confirmed that the mechanism of the chemical conversion after chemical pretreatment of bamboo through the Fourier infrared spectrum. The results showed that the output cellulose increased significantly after the thermochemical pretreatment. The change rules for yield of cellulose and the removal rate of lignin under the different pretreatment condition had been indicated dilute alkali (NaOH) treatment effect is better than that of dilute acid (H2SO4) and glycerin. In addition, the effect is more remarkable under the condition of 135 ℃ than 117 ℃ in the same medium. The changes of degradation degree of hemicellulose with different processing conditions were the same. The infrared spectrum analysis provided that C—O—C asymmetric stretching vibration peak appeared in cellulose decomposition after heat treatment, and it is the obvious steep fall in hemicelluloses infrared absorption characteristic peaks, benzene ring characteristic absorption peak of lignin has been abated. It is prove that yield of cellulose increased significantly, degradation trend of hemicelluloses is obviously, removal effect of lignin has also been better. The analysis results of Fourier infrared spectrum are consistent with the standard measurement.