The phase diagrams of water-in-oil microemulsions are very important for preparation of nano-sized BaSO4 particles. In this work

the influences of temperature

surfactant and surfactantaid

salinity and composition of oil phase on stability of microemulsions systems (Triton X-100/n-hexanol/cyclohexane/water )were investigated by measuring the electric conductivity and formation of liquid crystal

while some quasi-ternary phase diagrams were drawn.It was found that the ratio of surfactantaid and surfactant had a significant effect on stability of microemulsions. With increasing temperature

the region of microemulsions in phase diagrams became smaller

which could be used for breaking the microemulsions.The mixture with a small amount of n-hexanol in cyclohexane was better than pure cyclohexane. This work provided the basic data for the preparation of BaSO4 using W/O microemulsions.