In this work, wavelength dependence of the absorption function of soot was experimentally studied. We used a technique developed in our team which consists to heat similarly the soot particles using two different laser excitation wavelengths. Thus, using two lasers with the same temporal and spatial irradiance profiles, it is possible to find combinations of the both lasers energies, below sublimation regime activation, insuring that soot particles absorb the same energies, reach the same temperature and emit the same Laser Induced Incandescence (LII) radiation [1]. Laser at 1064 nm is always chosen as a reference excitation and compared with a UV-visible wavelength (λi) such as 266 nm, 355 nm, 532 nm. In this way we can deduce the relative evolution of the absorption function E(mE,(1m0,6λ4in)m) versus wavelength.