Abstract: In order to find out the rule of hydrogen cyanide (HCN) formation from the nitrogenous compounds in tobacco during cigarette combustion, the effects of puffing temperature, oxygen content in puffing atmosphere and flow rate thereof, and heating rate on the HCN formation from the protein, proline and asparagine in tobacco were investigated with a cigarette smoking simulator. The results showed that: 1) Pyrolysis temperature, oxygen content in puffing atmosphere and heating rate obviously affected the HCN formation from protein, proline and asparagine, while the effect of carrier gas flow rate was slight. 2) Rich oxygen atmosphere, low burning rate and low circumstance temperature inhibited HCN formation from the pyrolysis of its precursors or tobacco.