Abstract: Starch, including amylose and amylopectin,is very important to quality and yield of tobacco leaf.To detect the content of starch in fresh tobacco leaves is significance for master the growth and quality of tobacco leaves.However,amylose and amylopectin in tobacco are difficult to determine.An improved method using HClO4 as extractant was established for fast and accurate determination of these two constitutes.The method included the following steps: grinding the cut fresh tobacco with liquid nitrogen,bleaching the sample uing alcohol-NaCl saturated solution,extracting the starch from tobacco with 40% HClO4,continuous flow analyzing at the wavelength of 600 nm and 570 nm for amylase and amylopectin,respectively.The amylose was colorized after sodium hydrate solution extraction while the amylopectin was colorized directly.The detection limits of amylose and amylopectin were 0.49 mg/g and 0.37 mg/g,respectively,the average recovery for amylose and amylopectin were 111.97% and 104.41%,respectively,and the relative standard deviation of the two starches was both less than 5%.