The dissolution of main active ingredients puerarin in Redix pueraria of different particle was studied in this paper.Redix pueraria was made into ordinary powder and ultra-fine powder with particles of 40-65 mesh,65-100 mesh,100-200 mesh,200-300 mesh and more than 300 mesh,respectively.Cotents of puerarin from different particles treated with water and 30% of ethanol were determined by high performance liquid chromatography(HPLC).The results were as following: the contents of puerarin from aboved particles were 2.68%,2.95%,3.03%,3.13%,and 3.20% respectively after treated with water,and 3.10%,3.17%,3.35%,3.55%,3.66% respectively after treated with methanol.The results showed that dissolubility of puerarin in Redix pueraria was increased with decreasing particle size and the content of purrarin in Redix pueraria treated with methanol were higher than that of treated with water.