The content of chlorine in tobacco determined by continuous flow analysis (CFA), the standard method described in YC/T 162-2002 and GB 13580.9-1992, is considerably different from that by other classical methods, such as Moore method, potentiometric titration and ion chromatography. Therefore, the various factors affecting CFA were investigated, optimized and improved: 1) a dialyzer was set in the analyzer; 2) the detecting wavelength was shifted from 480 nm to 490 nm; 3) the flow-through cell with 15 mm optical path was replaced by a 10 mm flow-through cell without bubble elimination; 4) the determined optimum coloring reaction time was about 665 seconds; 5) the flow scheme of instrument was redesigned. The results showed that: the disturbance from the background color of tobacco extract was eliminated; the detection period reduced from 160 seconds to 90 seconds; the content of chlorine in tobacco determined by the improved method was highly in accordance with that by the classical methods mentioned above, with RSD < 5% and t = 1.6278 < t1-a = 0.10/2 (n-1) = 1.7341. The improved method is fit for fast analysis of chlorine in tobacco.