Abstract: Experiments on pyrolysis of cellulose added with calcium chloride (CaCl2) were done on a thermogravimetric (TG) balance to study the catalytic mechanism of the process. Compared with the TG curves of pure cellulose pyrolysis, those added with CaCl2 show that CaCl2 has a strong effect on the formation of char, which increases the char yield from 5% to above 10%. In addition, it affects the formation of active cellulose by moving TG curve towards lower temperature, and leads to a small weight loss peak at the initial stage of decomposition process, which reveals the emission of small gas are improved in the process of de-polymerization of long chain biomass molecule. By kinetic analysis, the pyrolysis process of cellulose with CaCl2 is divided into three stages, respectively, corresponding to the formation of AC, carbonization and conversion into volatiles, which control the weight loss process sequentially. Based on the Broido-Shafizadeh model, those kinetic parameters calculated by narrow temperature zone method show that CaCl2 enhances all these three reactions. Especially in the low temperature the formation of char is catalyzed strongly, whose active energy has a sharp decrease. Because of the catalytic selectivity of CaCl2 on different reactions, CaCl2 has an especial effect on the formation of char, and decreases the emission of gas during the carbonization process, which indicates the char catalyzed by CaCl2 has high aliphatic degree.