【Objective】 Cadmium (Cd) is the heavy metal pollutant with the highest over-limit rate in paddy soil in China. The bioavailability and mobility of Cd are affected by dissolved organic matter (DOM) in the soil. Paddy fields are important food production areas in China. As an important ecological agriculture mode in the rice industry, integrated planting and breeding of rice fields is of great significance to rural revitalization. The modification of paddy field environments and fishing can change DOM, but the complexation process between soil DOM and Cd²⁺ in paddy soil and during integrated planting and breeding of rice field process has not been clearly understood. 【Method】 In this study, the complexation process between DOM and Cd²⁺ in rice-shrimp cultivation (RS) and rice monoculture (CK) systems was investigated using a comprehensive array of analytical techniques, including ultraviolet-visible absorption spectrum (UV-Vis), 3D fluorescence spectroscopy, synchronous fluorescence spectroscopy, parallel factor analysis (PARAFAC), 2D correlation analysis (2D-COS), and the modified Stern-Volmer binding reaction model. Herein, RS was taken as an example of integrated planting and breeding of rice fields.【Result】 The PARAFAC analysis showed that soil DOM components of RS and CK were similar, including 1 tryptophan (C1) and 3 humus components (C2, C3, C4). Compared with CK, the proportions of C2 and C4 in soil DOM of RS were lower, while C3 was higher, and C1 was not significantly different. The UV-vis spectrum showed that DOM absorbance in CK was higher than in RS, with the absorption peak mainly located at 200-230 nm. With the increase of Cd²⁺, the change of UV-vis spectrum and UV254 was significantly different between RS and CK. Synchronous fluorescence spectra and 2D-COS analysis showed that paddy soil DOM fluorescence intensity changed with the increase of Cd²⁺, three absorption peaks were found by synchronous fluorescence spectra in DOM of paddy soil, which were the peak of tryptophan at 270 nm and the humus peak at 310 nm and 370 nm, respectively. The binding order between soil DOM and Cd²⁺ in RS was humus (310 nm), tryptophan, and humus (375 nm), respectively. However, in CK, the binding order was tryptophan, humus (375 nm), humus (310 nm). In the Stern-Volmer binding reaction model, the fluorescence intensity of C1 and C4 decreased with the increase of Cd²⁺, but the fluorescence intensity of C2 and C3 was unstable, which showed that the complexation of humus components C2 and C3 with Cd²⁺ had instability. This also led to the failure of fitting C2 and C3 in the model. The complexation constants lgK of C1 and C4 in the soil DOM of RS were 4.25 and 5.03, which were higher than in CK.【Conclusion】 The soil DOM in RS and CK mainly consisted of humus and the material composition ratio of soil DOM in RS was different. The complex process of DOM and Cd²⁺ in paddy soil belonged to static quenching and the aromatic structure affected the stability of DOM and Cd²⁺ complexation. Also, RS influenced the binding ability of tryptophan and fulvic acid DOM to Cd²⁺ whereas the instability of the complexation of humus with Cd²⁺ and the complexation of C4 with Cd²⁺ can enhance the bioavailability of Cd in soil. The results of this research can provide a scientific reference for the study of soil Cd pollution mechanism and pollution prevention in paddy fields.