Abstract: Thermogravimetric mass spectrometry was used to investigate the pyrolysis features of tobacco stem. The effects of temperature rise rate and particle size on the tar product precipitation characteristics were analyzed in a nitrogen atmosphere. The results illustrate that the primary tar products during the pyrolysis of tobacco stem are benzene, toluene, aniline, phenol, and furfural. When 80 mesh tobacco stem particles were heated at a rate of 20 K/min, the relative accumulative amounts of tar products are 240.55×10^-12, 184.29×10^-12, 93.71×10^-12, 147.50×10^-12, and 154.64×10^-12 A/mg, respectively. Benzene and toluene are mostly precipitated in the pyrolysis stage of lignin, furfural is mainly released product in the pyrolysis stage of hemicellulose and cellulose, while phenol is precipitated throughout both stages. The intensity of tar products from tobacco stem pyrolysis increases with the rise of heating rate. The output of tar from tobacco stem pyrolysis with 80 mesh size is the highest, and the output amount of tar from tobacco stem pyrolysis with 150 mesh size is the lowest.