Phytoplankton specific absorption coefficient is an important optical parameter associated with phytoplankton biomass and absorption spectrum. The quantitative analysis of specific absorption coefficients of phytoplankton populations makes up for the deficiency of specific absorption spectra of phytoplankton populations in Yellow Sea and Bohai Sea, and provides a new idea for monitoring the phytoplankton population concentration. Combined with the phytoplankton absorption coefficient and pigment concentration data collected during the cruise in Yellow sea and Bohai Sea in June, 2016, CHEMTAX software is used to analyze the concentrations of eight dominant alga species in Yellow Sea and Bohai Sea. The multiple linear regression analysis of the absorption coefficient and concentration data of algal species is carried out by using the LOO-CV method, the specific absorption spectra of each algae are extracted, and the total absorption spectra are reconstructed. The results show that the model inversion is effective, and the reconstructed absorption spectrum is consistent with the measured spectra in blue and red wavebands. In addition, when analyzing the contribution of dominant alga species to phytoplankton absorption coefficient, it is found that among all dominant alga species, the dinoflagellate gives the greatest contribution to phytoplankton absorption, followed by cyanobacteria.