Objective:To study the formula of triptolide (TRI) self-microemulsifying drug delivery system (SMEDDS) and evaluate the pharmaceutical properties.Methods:The formula and preparation process of triptolide self-microemulsion were screened by the solubility test and pseudo-ternary phase diagram.With the average particle size and self-microemulsifying time as the indices,the further formula optimization of triptolide self-microemulsion was carried out.The pharmaceutical properties of triptolide self-microemulsion were evaluated.Results:The optimal formula of TRI SMEDDS was as follows:the amount of medium chain triglycerides (MCT) was 20%,that of polyoxyethylene castor oil (EL-35) was 40%,and that of polyethylene glycol 400 (PEG-400) was 40% in the oil phase.The average particle size was 43.48 nm,and the time of self-microemulsification was less than 30 s.Conclusion:The average particle size and the appearance of triptolide self-microemulsion are accordance with the requirements of pharmaceutics.Triptolide self-microemulsion has good sustained-release effect,which lays foundation for the further study on pharmacodynamics.