The synthesis process of doped photopolymer has a significant impact on its properties. The tradional optimization method for the synthesis process of doped photopolymers depends on experimental parameters and experimental experience. A method for quantitatively monitoring and optimization of the synthesis process of doped photopolymers by absorption spectrum is presented in this paper. The absorption spectra of samples in different steps of the preparation are measured and analyzed. The change rule of the absorption spectra in preparation process is revealed. Quantitative monitoring of the progress and the synthesis rate of photopolymers could be realized by the proposed method. This method brings new possibility to quantitative optimization in the preparation process of doped photopolymers.