Nicotine and its salts adsorbed on silica gel are employed to simulate the nicotine release behaviors of reconstituted tobacco particles (RTPs). Thermogravimetric analysis (TGA) was applied to provide an overview of the thermal behaviors of the nicotine, its salts and the RTPs. Diffuse reflectance infrared spectroscopy (DRIFTS) measurements of pyrolysis processes were performed on a FTIR spectrometer equipped with an in-situ DRIFTS reaction cell and a MCT/A detector. Firstly, the amine groups of nicotine and its salts are mainly adsorbed on the isolated hydroxyl groups of silica gel. Secondly, three adsorption modes of nicotine have been established. Finally, smoking machine was applied to study the release behavior of nicotine from the reconstituted tobacco particles (RTPs). The interaction between nicotine and the adsorbent is identified. Our results show interesting observations on thermal release of nicotine from the different substrates, proving the adsorption and thermal release of nicotine and it salts from RTPs, which have a guiding significance for the development of heat-not bum cigarettes.