In order to explore the influence of the degree of complete combustion on the conventional smoke index in the smoldering state of cigarettes, the actual flammability rate and free burning rate of 50 different cigarettes in China were determined by self-made equipment, combined with the analysis of conventional smoke components in gas chromatography.The results show that: ① The actual flammability rate is significantly negatively correlated with the free combustion rate, that is, the more complete the smoldering of the cigarette, the slower the free burning speed. ② The actual flammability rate is significantly positively correlated with total particulate matter (TPM), nicotine, tar, and suction port number in conventional flue gas, among which TPM has the strongest correlation; Free burning speed and TPM, the indexes of nicotine, tar and suction mouth were all significantly negatively correlated, and the correlation with TPM and tar was strong. Comprehensive analysis indicates that the more complete smoldering of cigarettesis, the slower the free burning speed has, with more the number of suction ports, and the tar content higher.