Abstract: In order to improve the accuracy to determine reducing sugar contents in tobacco by continuous flow method, the test parameters described in the domestic tobacco industrial standard YC/T 159-2002 were optimized via an AA3 continuous flow analyzer. The optimized conditions were shown as follows:0.20 mol/L hydrochloric acid solution was used as the activated water in red/red pipeline, the concentration of sodium hydroxide solution was reduced to 0.35 mol/L, and the temperature of the heating tank was lowered to 79℃. The results showed that:1) Adopting the optimized method, the correlation coefficient of the standard curve was 0.999 9, the limit of detection and the limit of quantitation were 0.006 3% and 0.021 0%, respectively. The relative standard deviations (RSDs) of intra-and inter-day were less than 5% and the spiked recoveries ranged from 96.88% to 102.86%. 2) F test indicated that there was no significant difference between the results determined by the optimized method and the standard method. The optimized method could continuously and accurately determine the content of reducing sugar in tobacco by 60 cups (40 cups more than the standard method).