Abstract: Abstract: The objectives of this study were to understand the role of carbohydrate metabolism in the enlargement of tuberous roots in Rehmannia glutinosa, and to provide a foundation for improving the yield and commercial grade of R. glutinosa. The content of soluble sugar was determined by anthrone colorimetry, and the contents of monosaccharide and oligosaccharide were determined by HPLC. Conditions for determination of monosaccharide content: mobile-phase acetonitrile-water (85:15), flow rate 1.0 mL/min, column temperature 40℃; for oligosaccharide content: mobile-phase acetonitrile-water (70:30), flow rate 0.5 mL/min, column temperature 25℃; for ELSD: gain 300, drift tube temperature 40℃, flow rate of nitrogen gas 30 psi, and spray pattern was cooling. The results showed that (1) in the leaves, soluble sugar content was increased in the cultivar compared with the wild variety; oligosaccharide content was increased at elongate period and rapid growth period, and was higher than that of the wild variety. (2) In tuberous roots: the content variations in both varieties were roughly similar; the cultivar showed obviously higher contents of fructose, glucose, stachyose and starch than the wild variety, while the wild variety showed higher sucrose content than the cultivar. The leaves of the cultivar showed higher photosynthetic capacity. During growth period, the decrease of sucrose content in tuberous roots could raise the gradient of sucrose contents between the “source” and the “sink”. This variation would benefit the transportation of photosynthetic assimilation products from leaves to tuberous roots, and thus boost the growth of roots and increase the yield of R. glutinosa.