Abstract: The mechanism of microemulsion forming of alcohols in dodecylsulfosate (AS),water and octane is studied,with particular emphasis on the effect of molecular weight,structure and concentration of alcohols, phase diagram of the four components: alcohol,AS,water and octane is used as a means of study,whereby the microemulsion regions as well as the maximum water content of microemulsions are found out. Some rules have been worked out and theoretical discussions have been attempted,which are believed to be of practical importance to tertiary oil recovery.