Abstract: In order to reduce the release rate of Strychnos alkaloids, emulsion solvent diffusion method was applied to prepare microcapsules of Strychnos alkaloids. Orthogonal experiment design was applied to optimize the preparation conditions using drug loading(DL), encapsulation efficiency(EE) and appearance of the microcapsules as the evaluation indexes. The in vitro release of Strychnos alkaloids was also studied. The results indicate that the optimal preparation conditions of microcapsules are as follows, mass ratio of strychnine alkaloids to capsule material 1∶2, mass concentration of capsule material 0.135 g/mL, emulsifier’s volume fraction 2%, and volume ratio of the organic phase to the aqueous phase 1∶5. The average encapsulation efficiency and drug loading capability of Strychnos alkaloids in the microcapsules prepared by three times parallel experiments are 53.99% and 18.25%, respectively.The microcapsules have good sphericity, fluidity and uniform size. The Strychnos alkaloids in the microcapsules slowly dissolve in artificial gastric juice.