Microwave method was used to extract Radix astragali extracts form p-cyclodextrin derivative.The capability of removing effect on nitrite with Radix astragali was determined.The optimum experiment conditions were studied.The capability of removing nitrite with Radix astragali flavone was determined by spectrophotometry under simulated human gastric juice.The optimum conditions was as follows:volume of 40%ethanol,microwave 260w,microwave extraction time 2 min.The capability of removing Radix astragali on nitrite was improved by HP-β-CD derivative and the clearance effect was increased from 43.9%to 60.6%.