Abstract: Effects of surfactants of Tween 20 , 60 , 80 , glyceryl monostearate and ethylparaben , cosufactants of ethanol , propylene glycol and butanol on microemulsions were described on pseudo -ternary. Results showed that, adding alcohol contributes to the formation of microemulsion, the higher the proportion of oil phase alcohol, microemulsion phase was larger, but the content of alcohol in surfactant phase was not need too much. The aqueous phase full microemulsion system was mainly dependent on the oil and dilute surfactant mass ratio Wo/Ws, in the caprylic acid monoglyceride/Tween 80/ethanol/water and caprylic acid monoglyceride/Tween 80/propylene glycol/water system, even when Wo/Ws >1, added a sufficient amount of alcohol could not form fully -diluted microemulsion system. Moreover, the complex of surfactant was not necessarily with synergistic effect. Finally, determine the microemulsion formulation as oil phase:glycerol mono -octanoate and propylene glycol, the mass ratio of 2∶1;surfactant phase:Twain 80 and ethanol mass ratio of 2 ∶1;double distilled water: water. The food grade glycerol mono-octanoate microemulsion phase area was 73.81% , with 3 infinite dilution tunnel. Study on the stability of the concentration of salt ions and pH showed that the microemulsion system, good stability in NaCl concentration in the range of 0.1⁰.6mol/L, and the influence of pH was small.