Abstract: Drug-loaded microspheres are usually used as a biophysically targeted delivery system.The morphology and size distribution of the microspheres are key effects on the efficiency in therapy.The microspheres could be prepared by the spray drying method, and the characterization could be controlled by varying the drying conditions.The whole preparation process is highly efficient, and suitable for commercialization.In this work,a case for preparation of the microspheres of tanshinone (TAN) solid dispersions was studied, and the mechanisms of morphology and size control of microspheres during the spray drying process were investigated.The effects of inlet temperature，concentration and components of precursors, and feed rate on the morphology and size distribution of products were studied.The results showed that the morphology of the dry products depended on the inlet temperature, the components of precursor and feed rate.Among them,temperature was the most important factor.The size of microspheres was mainly controlled by the concentration of the precursor.This work might be a reference for morphology and size control of targeted drug delivery microspheres by the spray drying method.