Abstract: In order to investigate the aerosol particle size distribution of tobacco heated at low temperature, a test method for characterizing the particle size distribution of aerosol was developed by a combined system based on a steady state pyrolysis device and an impingement sampler. The effects of temperature, the first stage inlet air flow, the second stage inlet air flow and tobacco sample type on the aerosol particle size distribution were studied. The results showed that: 1) The combined system was suitable for analyzing the characteristics of aerosol particle size distribution of tobacco heated at low temperature. 2) Comparing with elevating temperature, increasing the first stage and second stage inlet air flow, especially increasing the first stage inlet air flow, was more effective in inhibiting particle agglomeration, pushing particle distribution towards smaller side, and reducing mean mass diameter of aerosol. 3) Under the same low-temperature pyrolysis condition, tobacco samples in the order of mean mass diameter of aerosol were burley tobacco > flue-cured tobacco > expanded cut tobacco ≈ reconstituted tobacco > oriental tobacco > expanded cut stem.