Abstract: In order to avoid the detrimental effect of Na⁺ to the determination of ammonia by ion chromatography, a new method was established and applied for ammonia determination in mainstream cigarette smoke by post-column derivatization with ninhydrin by using amino acid analyzer. The pretreatment for tobacco smoke samples was carried out according to the industrial standard method (YC/T 377-2010). The chromatographic conditions were optimized to achieve separation and post-column derivatization of ammonia by using SYKAM LCAK06/Na (4.6×150 mm) ion chromatogram column and Na⁺ buffer system. The results showed that the linear range of the proposed method was 0.1001-1.2019 μg/mL, the detection limit was 0.145 μg/cig, with the RSD% and the average recovery rate were 1.25% and 97.6%, respectively. This method has a distinct advantage in interference of Na⁺ and is adequate for quick and sensitive determination of ammonia in mainstream cigarette smoke.