Using Fourier transform infrared(FT-IR) spectroscopy technique, the carbonyl stretching vibration bands of AOT in sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/isooctane/water reverse(W/O) microemulsions system have been investigated by least square curve fitting. The results indicate that an asymmetric adsorbed peak of carbonyl stretching vibration of AOT molecule is situated in(1739 ± 1) and(1725 ± 2) cm-1. The two peaks correspond to different carbonyls in gau-che conformation and trans conformation of AOT molecules, respectively. With different water contents(W0), the variations of peak intensity ratio(Ir1 = I1739/I1725) reflect the change of the ratio for the two conformation populations and the variations of the effective head-group area of AOT mo-lecule have relations to the ratio of two conformation populations.