The conditions for the formation of microemulsion during the saponifioation of D2EHPA (1 M)-secondary ootyl alcohol (15%)-kerosene by four different oonoentrations of NaOH, NH₄0H or KOH have been systematically studied. Twelve phase diagrams wore constructed, the oonduotivities, visoosities and water contents of the organic phase were determined for each saponifioation process. It was found that they have maximum values at the equivalent point. The effect of the presence and content of the long-chain alcohol on the formation of mioroemnlsion has also bin studied. In the saponifioation systems with NaOH or KOH, the presence of the long-chain alcohol is necessary, ita content mast be higher than 5%,otherwise the formation of the third phase cannot be avoided.