Hydroxypropyl-β-cyclodextrin (HP-β-CD) was used to improve water solubility of Res. The preparation conditions of Res/HP-β-CD microcapsule by spray drying method were optimized, and Res/HP-β-CD microcapsule was confirmed by UV, IR and SEM. The results showed that optimum preparation conditions of Res/HP-β-CD microcapsule were mass ratio of Res to HP-β-CD for 15, stirring at 30 ℃, feed flow rate for 2.1 mL/min and inlet-air temperature for 140 ℃. The rate of drug-loading and the solubility of Res were 15.18% and 12.75 g/L, respectively, under the optimum conditions. UV, IR and SEM tests of Res/HP-β-CD microcapsule demonstrated that the aqueous solubility of Res increased due to the microcapsule formation between Res and HP-β-CD by hydrogen bond and hydrophobic forces, and the decrease of particle size.