The absorption of atmospheric aerosol particle is weak, but it affects earth′s radiation balance and atmospheric high energy laser transfer, so its precise measurement is paid more and more attention. By the analysis alteration of temperature distribution and refractive index which induced by pumping laser, the relationship of photo-thermal phase, effective absorption coefficient and excited time is deduced. Then phase generated carrier (PGC) algorithms for measuring phase change information is declared. It is also calculated that several photothermal effect of three typical aerosols with different absorbing capabilities which irradiated by pumping laser at two wavelengths. Then, the superiority of PGC algorithms is displayed, including its demodulation precision and noise elimination with calculation and error analysis. The experimental research of PGC algorithms is done.