The thermal decomposition behaviors of chlorogenic acid at different atmospheres and the content distribution of phenol in its pyrolysis products were investigated by thermogravimetry（TGA）and pyrolysis gas chromatography/mass spectrometry（Py/GC-MS）.The major mass loss temperature zone was obtained by thermal gravimetric analysis at nitrogen atmosphere,and the pyrolysis reaction of chlorogenic acid was investigated under inert（helium）and aerobic atmospheres（the nitrogen-oxygen mixture containing 9%oxygen）,respectively,at four typical temperature points selected from the major mass loss temperature zone,together with the other three points chosen from the high temperature combustion zone when a cigarette was ignited.The results indicated that the pyrolysis product in the presence of helium or nitrogen-oxygen mixture did not show any significantly difference,but the product sorts in nitrogen-oxygen mixture were a few more than those in helium with the increase of temperature.The relative content of the main pyrolysis product,phenol did not changed specially except at 300 ℃ and aerobic atmosphere.The major mass loss temperature zone was divided into five temperature ranges by an interval of 100 ℃.In each temperature range,the evolved gas was absorbed by 10 mL 1% acetic acid solution and then analyzed by HPLC.The results indicated that the main pyrolysis product of chlorogenic acid was phenol.Furthermore,the pyrolysis content of phenol changed with the varication of the temperature.This study provided a reference for the analysis of pyrolysis of tobacco ingredients in cigarette burnning.