Propylene glycol has a good ability informing microemulsions with oleic acid and Tween 80 and itsaqueous solution has a good solubility of STZL which can form a con-centration gradient. So oleic acid, Tween 80 and Propylene glycolwere subsequently used as the oil phase, surfactant and cosurfac-tant for the formulation of microemulsions containing STZL in thisstudy.