Abstract: To explore the subcellular distribution and detoxification mechanism of cadmium (Cd) in Capsicum annuum L. (capsicum) regulated by calcium (Ca) under different acids and alkalis, a pot experiment was used to analyze the subcellular distribution of Cd in capsicum tissues, the changes in root cell wall structure, and the distribution characteristics of Cd in its main components under the interaction of different acid-base conditions and calcium addition. The results showed that the cell wall and soluble components of capsicum tissues were the main subcellular enrichment sites of Cd. Still, their proportions differed in different tissues, and Cd in organelles only accounted for 1%~13%. Pectin and cellulose were the main substances that adsorbed and fixed Cd in root cell walls, which played important roles in the process of Ca regulating the adsorption of Cd on cell walls. FTIR spectrum showed that the interaction between Ca and Cd induced polysaccharide remodeling on the cell wall. In conclusion, the increase of Ca concentration was beneficial to the stability of cell wall structure, enhanced the retention and compartmentalization of Cd²⁺ by cell walls and vacuoles, reduced the transfer of Cd²⁺ to organelles and aboveground tissues, and enhanced the tolerance of capsicum. Different pH conditions affected the distribution of Ca and Cd in cell components by regulating the absorption of Ca and Cd by roots. The regulation of Ca on the subcellular distribution characteristics and detoxification mechanism of capsicum Cd was significantly influenced by different pH conditions, Ca concentration, and their interaction.