Abstract: The mass change and gaseous products of pyrolysis of black tea polyphenols (RM) and green tea polyphenols(YS) were tested by using simultaneous thermal analyzer(TGA/DSC), on-line Fourier transform infrared spectrometer(FT-IR)in conjunction with mass spectroscopic(MS)instrument. The chemical compositions of solid residue at different heating temperatures were also monitored, and the pyrolysis mechanism of tea polyphenols was analysed. It was observed that tea polyphenols could be classified as aromatic compounds with rich side chains, mainly consisting of C, H and O elements as well as tiny N element. The weight loss of pyrolysis below 200℃ was essentially the result of evaporation of free water and bound water. Pyrolysis began at about 200℃, which could be attributed to the stability of the side chains in the chemical structure of the samples. At the temperatures between 200 and 350℃, tea polyphenols dramatically decompased by breaking side chains in their structure and the recombination of free radicals, leading to the generation of enormous gaseous products such as H2O and CO2, etc. At the temperatures between 350 and 800℃, the pyrolysis reactions became sustainably slow, highlighting the generation and accumulation of more stable chemical structure containing polycyclic aromatic hydrocarbons in the pyrolysed residues. The established understanding provides the guidelines for effective utilization of tea polyphenols and the development of new application prospects in fire prevention and protection field.