A multi-peak Gaussian fitting method is successfully used to distinguish two absorption peaks in UV-vis absorption spectrum. The multi-peak Gaussian fitting method for UV-vis absorption spectrum is a good method to determine critical micelle concentration (CMC) of surfactant. The values of CMC are 0.151, 0.164 and 0.181 mM for sodium dodecylbenzene sulfonate (SDBS) at the concentrations of n-decyl-β-D-glucopyranoside (DGS) and aniline green (AG) fixed as 1.0 and 0.025 mM, which are determined by a ratio of integrated absorbance of AG monomer absorption peak to AG dimer absorption peak (A1/A2), a wavelength shift of absorption peaks (Δλ) and a half-width (w1,w2) of absorption peaks , respectively. The CMC is similar around the room temperature from 306.2 to 327.2 K.