Abstract: Peat soil is rich in organic matter, which is the main reason for its poor engineering properties. The content and compositions of organic matter of peat soil lead to the various physical and mechanical properties of this kind of soil. In order to clarify the influence of organic matter content, a series of laboratory tests are conducted on dozens of groups of amorphous peat soil samples with different organic matter content, and the laws of physics, deformation, strength and permeability with organic matter content are systematically analyzed. In order to compare the difference in engineering properties caused by the different organic matter components, the experimental data of the fiber peat soil from domestic and foreign literatures are collected and compared systematically with the physical and mechanical indexes of the amorphous peat soil. The results show that there is a certain linear relationship between the basic physical and mechanical indexes of the amorphous peat soil and the organic matter content. Among them, the initial void ratio (e₀), natural moisture content (w₀), liquid plastic limit (w_p, w_L), cohesion (c) increases linearly with the increase of the organic matter content. Specific gravity (G_s), consolidation coefficient (C_v) and internal friction angle (φ) decrease with the increase in organic matter content. Compared with the amorphous peat soil, the fiber peat soil is characterized by small specific gravity, high water content and a large void ratio. In terms of shear strength, the cohesive force of the amorphous peat increases with the increase of organic matter content, which is slightly higher than that of the fiber peat soil. The internal friction angle has a downward trend with the increase of organic matter content, which is about 1/5～1/14 that of the fiber peat soil. In terms of permeability, the initial permeability coefficient (k_v0) and permeability index (C_k) of the amorphous peat soil decrease with the increase in organic matter content, and are generally smaller than those of the fiber peat soil.