Abstract: Given the scarcity research on the activation of selenium (Se) by organic acids in acidic soils, a pot experiment was conducted to investigate the effects of different amounts of exogenous compound organic acids (COA) on the the absorption and transport of Se in rice as well as soil properties under acidic soil conditions, providing technical support for the production of Se-enriched rice. This study consisted of four treatments: 1) treatment without COA (CK), 2) treatment with 0.23 mg∙kg^–1 COA (LOA), 3) treatment with 1.14 mg∙kg^-1 COA (MOA), 4) treatment with 2.28 mg∙kg^–1 COA (HOA). The results showed that no significant difference in grain yield and aboveground biomass of rice was observed between CK and treatments with COA addition under the equal application of Se (0.5 mg Se∙kg^–1). However, LOA and MOA treatments significantly increased the Se content in rice grain and the accumulative amount of Se in the whole plant compared with the control, with increments of 28.7%, 27.3% and 40.1%, 34.1% respectively. In contrast, the HOA treatment significantly decreased the Se content and accumulation in rice stems compared with the control, with reductions of 23.5% and 46.7% respectively, indicating that the LOA and MOA treatments can effectively enhance Se absorption and transport, while the HOA treatment inhibits the transport of Se from the roots to the aboveground stems. Additionally, the COA addition treatments significantly increased the available phosphorus content in the rhizosphere soil and the available Se content in the non-rhizosphere soil, decreased the available sulfur content in both the rhizosphere and non-rhizosphere soils, and enhanced the activities of catalase (CAT) and peroxidase (POD) in the plant roots. Particularly, the medium-dose combined organic acid treatment significantly increased soil urease activity (UE). The LOA treatment reduced the dissolution effect of root activity on kaolinite minerals, while the HOA treatment promoted it. LOA treatment reduced the dissolution effect of root activities on kaolinite minerals, while HOA promoted the dissolution effect of root activities on kaolinite minerals. Principal component analysis indicated that soil UE activity and root CAT activity made significant contributions to the absorption and accumulation of Se in plants. In conclusion, exogenous addition of 0.23–1.14 mg∙kg^–1 of COA can improve the availability of soil Se, enhance the activities of CAT and POD in rice roots, and significantly increase the Se content in various parts of rice (2.52–8.56 mg∙kg^–1) and the Se accumulation in plants (177.2–185.2 ug∙plant^–1).This provides new ideas and approaches for effectively enhancing the Se content in rice grains and has important theoretical and practical significance for meeting the human Se nutritional health needs.