【Objective】Dissolved organic matter (DOM) plays a crucial role in maintaining soil carbon cycling and ecological functions. The accumulation of microplastics (MPs) in agricultural soils may alter the composition and stability of DOM. However, the mechanisms by which MPs of different polymer types affect DOM characteristics in soils with distinct physicochemical properties remain unclear. 【Method】In this study, two representative paddy soils, including acid paddy soil from Jinhua (JH, pH 5.03) and alkaline paddy soil from Cixi (CX, pH 8.26), were used as test soils. A 60-day microcosm incubation experiment was conducted by adding 0% and 0.5% of polyethylene (PE), polyvinyl chloride (PVC), and polylactic acid-Poly (butyleneadipate-co-terephthalate) (PLA+PBAT, Bio) MPs to investigate the effects of different MPs on soil basic physicochemical properties and DOM characteristics. Ultraviolet-visible (UV-Vis) spectroscopy and Three-Dimensional Excitation-Emission Matrix combined with parallel factor analysis (PARAFAC) were used to characterize variations in the DOM aromaticity, molecular weight, and fluorescent components under different treatments. 【Result】The results revealed that MP-induced effects were more pronounced in acidic JH soil than in alkaline CX soil. Among the treatments, Bio microplastic exerted the strongest influence. Compared to the control, Bio treatment in JH soil increased pH, dissolved organic carbon (DOC) concentration, and spectral slope (SR) by 2.09%, 4.58%, and 8.26%, respectively, while PE and PVC showed relatively minor effects. In the early stage (15 days), MPs significantly decreased SUVA254 values in JH soil, suggesting enhanced degradation or transformation of aromatic DOM components. This inhibitory effect gradually diminished over time. In contrast, no significant effects were observed in CX soil under any treatment. Furthermore, JH soil exhibited continuous declines in pH and SUVA values and an increase in SR during the incubation, indicating a trend toward lower molecular weight and simpler DOM structures. Meanwhile, CX soil maintained relatively stable DOM characteristics throughout the experiment. 【Conclusion】The impact of MPs on soil DOM was strongly influenced by both polymer type and soil properties. Biodegradable MPs, such as Bio, had a more substantial effect on DOM structure than traditional MPs such as PE and PVC. Acidic and coarser-textured JH soil was more vulnerable to MP interference and temporal changes, resulting in increased DOM reactivity and instability. In contrast, alkaline, fine-textured CX soil exhibited greater resistance to MPs-induced perturbations and maintained higher DOM structural stability.