【Objective】 Soil components serve as the material basis determining soil properties and heavy metal behaviors. However, the effects and mechanisms of different soil components on cadmium (Cd) adsorption performance, speciation, and bioavailability in purple soil remains elusive. 【Methods】This study employed selective removal and exogenous addition methods, combined with adsorption-desorption experiments, sequential chemical extraction, and pot bioassays, to investigate the effects of core components of OM (humic acid, HA and fulvic acid, FA), iron oxides, and manganese oxides on Cd adsorption performance, speciation, and bioavailability in purple soil.【Results】 The results show that there are significant differences in the effects of the various components of purple soil on soil properties: the removal of organic matter (ROM) and iron oxides (RFe) significantly increased soil pH and specific surface area (SSA), while the removal of manganese oxides (RMn) had the opposite effect; the removal of each component significantly reduced soil cation exchange capacity (CEC), charge quantity (SCN), and density (σ0), with the effects of RFe and RMn being the greatest; the addition of exogenous components had a significantly weaker effect on soil properties than component removal, and only the addition of organic matter-containing components (AHA and AFA) could increase soil pH and CEC, but significantly reduce SSA; the addition of manganese oxides (AMn) significantly increased SSA. The changes in soil components and properties regulate the environmental behaviors of Cd: ROM and RFe significantly enhanced the adsorption capacity and strength of soil Cd, while RMn had no significant effect; in the component addition treatments, only AHA and AMn could enhance the Cd adsorption capacity by soils. The availability of Cd (Avail-Cd) in purple soil is constrained by its occurrence form and has no significant correlation with adsorption capacity; among the various forms of Cd in the soil, only exchangeable Cd (EX-Cd) positively contributes to Avail-Cd, while carbonate-bound (CA-Cd), organic-bound (OM-Cd), and iron-manganese-bound (FeMn-Cd) all show negative contributions. ROM and RFe, as well as AHA, promote the transformation of EX-Cd to above less labile forms, thereby reducing soil Avail-Cd contents by 39.30% to 96.80%; while RMn, RFe-Mn, and AFA treatments act the opposite, significantly increasing Avail-Cd contents by 2.38 times to 2.91 times.【Conclusion】 The pot experiment confirmed that the accumulation of Cd in pakchoi (Brassica chinensis L.) is mainly regulated by the availability of soil Cd. Changes in soil components alter the biological availability of Cd mainly by adjusting soil pH, CEC, OM, SSA and thereby the distribution of Cd forms in soils. This study clarifies the regulatory effects and mechanisms of soil key components on Cd bioactivity, providing a theoretical bases for soil pollution remediation and management.