Abstract: The organic matter is an important symbol of peaty soil which is different from soft clay. The content of organic matter directly affects the physiochemical properties of peaty soil, and further affects its consolidation characteristics. Based on the researches of domestic and foreign scholars, the linear correlations between the content of organic matter with density, water content and specific gravity are analyzed. The void ratio of water and organic matter in the special four-phase model for peaty soil is deduced by combining the specific gravity of the inorganic solid phase with the mean specific gravity of the solid phase. Furthermore, by considering the effect of compression of organic matter on the consolidation characteristics of peaty soil, the compressive deformation model for organic matter is coupled with Terzaghi's one-dimensional consolidation theory, and the feasibility of the model is verified by comparing the calculated results with the experimental data.