Abstract: Antibiotics are widely used in daily life. At the same time, a large number of wastes containing antibiotics enter the soil through some ways, which brings serious harm to human health and soil environment. It is of great significance to explore the adsorption mechanism of antibiotic organic pollutants in the soil to prevent and control the soil pollution. In the present study, oxytetracycline (OTC) was selected as the target pollutant to investigate the effect of organic matter on sierozem soils based on the batch experiments. The research mainly included adsorption kinetics, thermodynamics and some influencing factors. The results indicated that the adsorption kinetic process could be divided into a fast (0-2 h) and slow (2-10 h) adsorption stages and reached equilibrium in 10 h. The adsorption kinetics could be better described by the pseudo-second-order model. For the adsorption thermodynamic process of OTC on sierozem soils at different temperatures, the fitting R² values of the Langmuir and Freundlich thermodynamic models were between (0.930-0.985) and (0.967-0.973), respectively. For the isothermal adsorption process of OTC with different initial concentrations on sierozem soils with organic matter, the fitting R² values of the Langmuir and Freundlich thermodynamic models were between (0.952-0.988) and (0.936-0.971), respectively, showing that both models explained the two adsorption processes well. The thermodynamic parameter analysis of OTC adsorption onto sierozem soils showed that the Gibbs free energy (ΔG^θ) was less than zero, while entropy (ΔH^θ) and enthalpy (ΔS^θ) were more than zero, indicating the adsorption of OTC onto sierozem soils was a spontaneous endothermic adsorption, which increased the degree of disorder during the process, and it was a physical adsorption. The addition of exogenous organic matter increased the adsorption capacity of OTC, and the promotion effect of self-made was greater than that of the commercial product. Meanwhile, the effect of HA was also greater than FA. The adsorption capacity of OTC onto sierozem soils showed a rapidly increasing trend when the initial concentration of OTC increased. The addition of Ca²⁺ and Na⁺ reduced the adsorption of OTC, and the higher the concentration and the valence state, the more obvious the inhibition effect. The effect of pH on the adsorption of OTC was small. The results showed that organic matter from different sources and types could promote the adsorption of OTC, but did not change the adsorption equilibrium time. HA had stronger hydrophobicity than FA, and had higher adsorption capacity for OTC. The pH value of solution had no significant effect on the adsorption of OTC, but metal cations with different valence and concentration had greater effect on the adsorption of OTC.