【Objective】Soil serves as a significant sink for microplastics (MPs), with the annual influx of MPs into soil being 4 to 23 times greater than that entering the ocean. Therefore, the assessment of the potential environmental effects of soil MPs cannot be ignored. As a non-natural carbon source, the precise impact of MPs on dissolved organic matter (DOM) in soil-crop systems remains unclear. 【Method】This study investigated the behavior of conventional MPs (polyethylene, PE; polystyrene, PS) and biodegradable MPs (polybutylene adipate terephthalate, PBAT; polybutylene succinate, PBS; polylactic acid, PLA) in soil using maize-cultivated pot experiments. We measured dissolved organic carbon (DOC) concentration, DOM fluorescence characteristics, and DOM molecular composition and properties in the system after MPs addition. 【Result】The results showed that MPs increased soil DOC content, as well as the humification degree and stability of DOM. Simultaneously, MPs decreased the H/C ratio of DOM molecules and the relative content of amino acid, carbohydrate, and protein-like molecules in the soil-plant system, while increasing the aromaticity index (AI) and nominal oxidation state of carbon (NOSC) values. 【Conclusion】Overall, this study reveals the impact of different types of MPs on DOM components in soil-crop systems, providing an important theoretical basis for the comprehensive assessment of the environmental risks of MPs and the formulation of plastic control policies.