AIM To prepare the moisture-proof granules of polysaccharides from Astragali Radix.METHODS Mixture design was adopted in the optimization of excipient proportion after moisture absorption determination of mixed powder of polysaccharides and seven excipients.With the influencing factors of ethanol concentration,ethanol amount,drying temperature and drying time,together with the evaluation indices of moisture absorption rate and non-forming rate,the preparation was optimized by orthogonal test based on single factor test.The critical relative humidities were then compared after drawing moisture absorption curves of polysaccharides,mixed powder and granules.RESULTS The mixed powder with an optimal ratio (1 ∶ 2) of polysaccharides to mixed excipients (46.3％ lactose,14.5％ mannitol and 39.2％ microcrystalline cellulose) was found to remain the moisture absorption rate of 11.6％ within 168 h.The optimal conditions were determined to be 70％ for ethanol concentration,0.125 times for ethanol amount,55 ℃ for drying temperature,and 60 min for drying time,the moisture absorption rate was 8.1％ within 168 h,and the non-forming rate was 11.46％.Compared with polysaccharides and mixed powder,the granules showed relatively lower initial velocity and acceleration (absolute value) of moisture absorption,and relatively higher critical relative humidity.CONCLUSION The granules of polysaccharides from Astragali Radix prepared by this method show a good moisture-proof effect.