Long-chain ionic liquids surfactants: n-alkyl-3-methylpyridinium bromide [Cnmpy][Br] (n: the carbon numbers of hydrophobic tails, n=12, 14, 16) was synthesized by condensation reaction using 3-methylpyridinium and n-alkyl bromide as raw materials. The ionic liquids surfactants were characterized by FT-IR and NMR (1H, 13C). The critical micelle concentrations (CMC) of surfactants were determined by employing conductometry and Du Noüy ring method. The effects of temperature, carbon chain length on the CMC were also investigated, and the micellization thermodynamic parameters were calculated. The antibacterial activities were screened for compounds against three bacteria. The results showed that the CMC values for [Cnmpy][Br] (n=12, 14, 16) was found to be 9.52, 2.32 and 0.591 mmol/L, respectively. The CMC value measured by Du Noüy ring method were 1.21 to 1.31 times lower than that by conduc-tometry, The relationship between the number of carbon atoms in alkyl chain and CMC value were in ac-cordance with the Stauff-Klevens rule. The variation of CMC values of the compounds with temperature were first decreased and finally increased. The ΔGm and ΔHm values of the [Cnmpy][Br] surfactants were negative indicated spontaneous and radiative nature of the micellization process. The results of antibacterial activities showed that the [C14mpy][Br] surfactants had most intense antibacterial activities against three bacteria. The diameter of inhibition zone was 25.0, 28.0 and 26.0 mm, respectively.