Objective:To establish an HPLC-ELSD method for determination of monosaccharide content in different processed Radix Rehmannia Praeparata and to study the effect of different processed method on monosaccharide content in Radix Rehmannia Praeparata. Method: HPLC-ELSD was applied to analyze the content of monosaccharide with prevail carbohydrate ES column (4.6 mm×250 mm

5 μm)

acetonitrile-water (75∶25) as mobile phase. The flow rate was 0.8 mL·min-1;column temperature was kept at 30 ℃;temperature of drift tube set at 65 ℃

gas flow 2.5 L·min-1and gain 1. Result: The D-glucose and D-fructose average recovery was 98.24% (RSD 2.18%) and 98.37% (RSD 2.11%) respectively. The content of monosaccharide in Radix Rehmanniae from Wenzhi

steaming and stewing by liqour were 1.62%

27.22%±2.74%

9.63%±2.05%

16.97%±2.62% respectively. Conclusion: The method is simple

accurate and reproducible. The content of monosaccharide in Wenzhi Dihuang was higher than that of steaming Dihuang and stewing by liqour. It provides an experimental basis to illustrate its processing mechanisms.