Abstract: Cadmium (Cd) is one of the most severe heavy metal pollutant in farmland soils in China. Soil dissolved organic matter (DOM) significantly influences Cd migration and transformation in soil environments, however, whether the relationship between Cd mobility, bioavailability, and DOM spectral characteristics in paddy soils is affected by the rice-crayfish coculture mode (RS) remains unclear. Therefore, this study used traditional rice monoculture (CK) as the control and RS as the research object. Using ultraviolet-visible spectroscopy and three-dimensional fluorescence spectroscopy, we analyzed changes in DOM spectral characteristics and composition in RS-mode soils during different rice growing stages early rice stage (T1), tillering stage (T2), booting stage (T3), and yellow ripening stage (T4). Correlation analysis and stepwise regression models were used to establish the relationships between soil DOM and exchangeable Cd (Cd_ex) content in the RS and CK modes. The results were as follows. 1) Compared with other growing stages, both modes exhibited the highest aromaticity and hydrophobic DOM at T4. The molecular weight of DOM under RS mode showed a decreasing trend during rice growing, with DOM in T4 being more biogenic-oriented. 2) Soil DOM in both the RS and CK modes primarily consisted of tryptophan-like components (C1), humus components (C2 and C3), and fulvic-like components (C4). However, the proportional distribution of these components showed no significant variation across different growing stages. The fluorescence index (FI) values of both CK and RS modes exceeded 1.9, whereas the humification index (HIX) values were below 4. The biological index (BIX) of RS mode (0.70–0.76) was higher than that of CK mode (0.62–0.66), indicating that DOM in both modes possessed endogenous native characteristics to some extent. 3) In both modes, Cd_ex content increased progressively along with the rice growing. However, the RS mode exhibited a lower Cd_ex content and smaller fluctuations from T2 to T4 compared to CK mode. The Cd_ex content in both modes showed significant or highly significant correlations (P<0.05 or P<0.01 or P<0.001) with HIX, the spectral slope ratio (S_R) and fulvic-like components (C4), demonstrating close associations between the Cd_ex content and the DOM humification degree, molecular weight, source, and composition. Stepwise regression analysis revealed that factors related to DOM molecular weight (E₂/E₃ and S_R) critically influenced Cd_ex content prediction providing a theoretical references for understanding the potential impacts of rice-crayfish coculture systems on soil Cd pollution.