In relation to the preparation of Langmuir-Blodgett thin film, four kinds of N-alkylpyridiniurn bromide were synthesized. The values of surface tensions of these materials, measured with a Traube stalagmometer, gave the relationship between the critical micells hydrophobic radical and between CMC and temperature. Values of thermodynamic properties(${Delta}H^0_m,;{Delta}S^0_m,;{Delta}G^0_m,$) for the formatoin of micelle were also obtained. Experiments gave the following results; at the temperature range between 40 and 60$^{circ}C, CMC of Hexadecyl-, Octadecyl-, Eicosyl-, and Docosyl-Pyridinium Bromide were $7.64{ imes}10^{-4}{sim}9.13{ imes}10^{-4},;3.85{ imes}10^{-4}{sim}4.60{ imes}10^{-4},;2.00{ imes}10^{-4}{sim}2.39{ imes}10^{-4},;and;1.07{ imes}10^{-4}{sim}1.28{ imes}10^{-4}$ mol/l, respectively. Surface tension, ${Gamma}_{CMC}$, of those were 33.49${sim}$36.00, 34.78${sim}$37.61, 35.49${sim}$37.61 and 38.76${sim}$55.80 dyne/cm, respectively, The relationship between CMC and the mumber of carbon atoms in the hydrophobic radical, N was expressed as follows : Log(CMC)=A-BN where A and B are constants. At the temperature range between 40 and 60$^{circ}C$, the change of Gibbs evergy (${Delta}G_m$) for one methylene group ($-CH_2-$) were -0.65RT, respectively, The minus values of enthalpy change (${Delta}H_m$) suggest that the formation of micelle is exothermic. Additionally, the overall increase in the entropy change (${Delta}S_m$) with respect to the temperature increase suggests that the formation of micelle is attained by a exothermic enthalpy directed process.