Abstract: OBJECTIVE To preparation testosterone undecanoate self-microemulsifying drug delivery systems (TU SMEDDS). METHOD The formulation of TU SMEDDS was obtained by pseudo-ternary phase diagram and the determination of self-microemulsifying efficiency. RP-HPLC was used to assay the contents of TU. The quality of TU SMEDDS was evaluated under the conditions of severe temperature and light test. RESULTS The medium of TU SMEEDS was composed of equi-weight of octyl decyl glycerate (ODO) as oil phase and two nonionic surfactants, Cremophor EL and Tween85, with the weight ratio of 1∶4 as emulsifying agents. This formulation can be rapidly emulsified in different aqueous. The TU content gave slight decrease under the 10 day severe light test while represented stability under temperature test. CONCLUSION The emulsifying agent of TU-SEDDS is using two mixture nonionic surfactants while no co-surfactants included, which is suitable to prepare soft capsules.