Abstract: In order to determine the delivery of HCN in mainstream cigarette smoke rapidly and accurately, the effects of smoke trapping method, coloring temperature and duration, pH value of buffer solution, 14 anions and 15 cations, and storing duration of sample solution on the results determined by a continuous flow analyzer(CFA) based on a coloring system with isonicotinic acid and 1, 3-dimethyl barbituric acid, were investigated.The results were compared with those determined by pyridine and pyrazolinone coloring system.The HCN deliveries of 50 domestic brand cigarette samples were determined by CFA with the tested coloring system.The results indicated that: 1) the highest trapping efficiency was obtained when particulate matter and gas phase was collected by a Cambridge filter and an absorbing flask with 30mL 0.1mol/L NaOH solution respectively, the HCN recovery was 99.1% with RSD of 4.3%;2) the highest spectral absorbance was achieved when the sample solution reacted with the isonicotinic acid + 1, 3-bimethyl barbituric acid system at a room temperature higher than 15℃ for 8 minutes;3) the preferable buffer solution was potassium hydrogen phthalate, pH5.3;4) HCN measurement was not affected by the trace ions in the smoke;5) the sample solution was stable within 6 hours after preparation;6) there was no significant difference between the results determined by these two mentioned coloring systems, however, the isonicotinic acid + 1, 3-bimethyl barbituric acid system was more environmentally friendly, stabler, simpler, more sensitive and precise;7) the HCN deliveries of 50 brands ranged from 26 to 147μg/cig, the average HCN deliveries of Virginia type and blended type cigarettes were 93.8 and 63.6μg/cig, respectively.The method is suitable for fast analysis of HCN in mainstream cigarette smoke of batches of samples.