Based on the investigation of the polysaccharide structure of cellulose by using Fourier transform spectrum analysis, the pyrolysis behaviour of cellulose was studied at a heating rate of 20 K/min by thermogravimetric (TG) analysis coupled with Fourier transform infrared (FTIR) spectroscopy. Experimental results show that the decomposition of cellulose mainly occurs at the temperature range of 550–670 K. The weight loss becomes quite slow when the temperature increases further up to 680 K and the amount of residue reaches a mass percent of 14.7%. The FTIR analysis shows that free water is released first during cellulose pyrolysis, followed by depolymerization and dehydration. Glucosidic bond and carbon-carbon bond break into a series of hydrocarbons, alcohols, aldehydes, acids, etc. Subsequently these large-molecule compounds decompose further into gases, such as methane and carbon monoxide.