Abstract: The micro- emulsion of chestnut flower oil was prepared by the emulsifying method of phase inversion and the effect of surfactant,co- surfactant,the ratio of surfactant with co- surfactant( Km) and oil phase on microemulsion formation were investigated by pseudo- ternary phase diagrams for determining the process parameters of chestnut flower oil micro- emulsion. The results showed that the best formula of chestnut flower oil micro-emulsion was polyethylene glycol stearate-15( HS-15) and glycerol as surfactant and co- surfactant,respectively,the Kmwas 2,and equal proportional ethyl oleate( EO) and oil as mixing oil phase.The micro- emulsion of chestnut flower oil prepared according above formula was O / W type. Moreover,the conductivity,viscosity and p H of the micro- emulsion characteristic parameters were investigated when the ratio of mixed surfactant with oil phase was7∶ 3 based on the best micro- emulsion formulations,they were 180.2 μs / cm,44.7 m Pa·s,and 6.66,respectively.Therefore,this study provided technical supports for preparing and applying the micro- emulsion of chestnut flower oil.