Abstract We have studied the effect of adding sucrose distearate (2C18SE) on the solubilization capacity of microemulsions formed in the water/C12EO6/n-decane system. Upon addition of 2C18SE to the binary water/C12EO6 system, a lamellar liquid crystal region developed. This suggests that the rigidity of the surfactant layer is strengthened. The solubilization of water and n-decane in the bicontinuous microemulsions increases about three times upon replacing 10% C12EO6 with 2C18SE; besides, the HLB temperature is not greatly affected by 2C18SE. On the other hand, sucrose monostearate (C18SE) does not have such a function. The effect of added 2C18SE on the solubilization capacity of the discrete droplet-type o/w or w/o microemulsions was also studied. The efficiency of the solubilization-improving effect is reduced when the system is far from the HLB temperature.