Abstract: The thermodynamic properties of microemulsion formed by six kinds of alkyl aryl sulfonates(AAS,synthesized in the laboratory) in the multi-component systems were investigated by dilution method.The influences of molecular structure,temperature,short chain alcohol,water content and salt concentration were respectively discussed.The results show that the increase of long alkyl carbon atom number(in alkyl aryl sulfonate molecule) causes the ΔG_o→i⁰ of the AAS/n-butanol/n-decane/water microemulsion systems decrease,along with the increase of the ΔS_o→i⁰,and facilitates the formation of the microemulsion.The ΔS_o→i⁰ and carbon atom number of alkyl chain are in linear relationship,with ΔS_o→i⁰=1.7975n+71.538.The ΔH_o→i⁰ is a constant.As the aromatic rings shift from the edge to the middle of the long carbonic chains,the ΔG_o→i⁰ of the microemulsion systems decreases,along with the decrease of ΔS_o→i⁰ and ΔH_o→i⁰,facilitating the formation of the microemulsion.With the increase of temperature,ΔG_o→i⁰ of the microemulsion systems increase,hindering the formation of the microemulsion.The increase of carbon atom number of the alcohol causes ΔG_o→i⁰ decrease,which enables the formation of the microemulsion.ΔG_o→i⁰ and carbon atom number of the alcohol are in linear relationship,with ΔG_o→i⁰=-2790.8n+7286.4(328 K).The increase of water content causes ΔG_o→i⁰ increase and the formation ability of the microemulsion decreases.ΔG_o→i⁰ and the volume of water are in linear relationship,with ΔG_o→i⁰=6697.8V-7170.4(318 K).The increase of salt concentration causes ΔG_o→i⁰ decrease,and the formation ability of the microemulsion increases.