In order to determine hydrogen cyanide (HCN) in mainstream cigarette smoke with autoanalyzer more accurately, the effects of formaldehyde, acetaldehyde, acetone and acrolein, as well as the concentration of formaldehyde on the determination system were examined, and the stability of HCN in diluted and undiluted trapping solution for gas phase and extraction solution of particulate phase was investigated. The results showed that: 1) formaldehyde had notable influence, however, acetaldehyde, acetone and acrolein had little, negligible influence on the determination system; 2) the determined value of hydrogen cyanide decreased by 7.38% and 13.51% in the presence of formaldehyde of 5.80 and 11.49 μg/mL, respectively; 3) formaldehyde had notable influence on the stability of the sample, and the other three compounds’ influence was negligible; 4) the stability of HCN in undiluted trapping solution for gas phase and extract solution of particulate phase was poor, which was obviously improved in diluted solutions; 5) the recovery of the method ranged from 100% to 104% with the relative standard deviation (RSD) of 1.11%, and the relative deviation between the HCN values by this method and ion chromatography was less than 5%.