The production and application of fluorinated surfactants containing long fluorocarbon chains have been restricted due to their environmental persistence and bioaccumulation. Thus seeking replacement products is in urgent needs. In this work, the oil-water interfacial tension of a perfluorobutyl-based cationic fluorinated surfactant, C4F9SO2NH(CH2)3NH(CH3)2+Cl- (PFB-MC), was investigated. PFB-MC was highly surface active in acidic aqueous environment. The effects of different kinds of additives, such as NaCl, hydrochloric acid, n-butanol, iso-butanol, n-pentanol, n-hexanol, and alkyltrimethylammonium chlorides (CnH2n+1N(CH3)3Cl, n = 12, 16, 18), on the interfacial tension of PFB-MC at n-heptane-water interface were studied. The surface tension of the aqueous mixtures of PFB-MC and CnH2n+1SO3Na (n = 4, 6, 8) were measured, as well as their interfacial tension against n-heptane. The interfacial tension of the mixture of PFB-MC and sodium dodecylbenzene sulfonate (SDBS) was also measured for comparison. The results showed that, the addition of relatively high concentration of NaCl, hydrochloric acid, or fatty alcohols could all reduced the oil-water interfacial tension of the system, however, the reduction of interfacial tension was only 1~3 mN/m; In contrast, the addition of CnH2n+1SO3Na brought the best synergism and could remarkably reduce the oil-water interfacial tension of PFB-MC by a reduction of 4~9 mN/m, and the interfacial tension decreased with the chain length of sodium alkane sulfonates; However, the interfacial tension of the mixture of PFB-MC and SDBS was rather high (18.6 mN/m for the clear phase ) because of the poor solubility.