Abstract: This work attempts to reduce the surface tension of organic solvents with oil-soluble fluorinated surfactants.Number of fluorocarbon chains in the surfactant molecule is increased thus to enhance density of the fluorocarbon chains adsorbed on surface layer of the organic solvents.Two series of fluorinated surfactants were synthesized:through the reaction of perfluorooctane sulfonyl fluoride with diamine (NH₂(CH₂)_{nNH2,n=2,3,6,10),the oil-soluble fluorinated surfactants,containing sulfonyl amido group as the spacer,with two fluorocarbon chains in one surfactant molecule were obtained;through the reaction of perfluorooctanoic acid with polyhydric alcohols (glycol,1,2-propanediol,glycerol and pentaerythrite),the oil-soluble fluorinated surfactants,containing ester group as the spacer with two,three and four fluorocarbon chains in one surfactant molecule were obtained respectively.The surface activity of the two series of fluorinated surfactants in ethanol,ethyl acetate,butanone and the ternary mixed solvent of ethanol,ethyl acetate and butanone were studied.The effects of molecular structure of surfactants and the type of organic solvent on their surface activity were observed.The results showed that there was no simple inevitability between surface tension reduction and the number of fluorocarbon tails.The configuration of the whole molecule was also important,and the type of these polar organic solvents could have significant influences on the surface tension of such surfactant solution.}