<p>The remediation of antibiotic-contaminated water relies critically on the rational design and development of high-efficiency photocatalysts capable of operating under visible light. This study aimed to develop calcium-doped BiOCl nanocomposites for visible-light photocatalysis. Samples with adjustable Ca²⁺ concentrations were prepared via hydrothermal synthesis followed by calcination, and their effectiveness in decomposing CIP was systematically investigated. The experimental results show a 1.51 times enhancement in CIP degradation efficiency for the Ca-doped sample (BOCl/Ca-10) compared to pristine BOCl. Characterization results reveal that Ca²⁺ doping induces beneficial adjustments in the electronic configuration and microstructure of BOCl, thereby optimizing its functional properties. The identification of •O₂⁻ as the primary reactive species was achieved through radical trapping experiments. Furthermore, calcium doping is established as an effective strategy for modifying BiOCl. As demonstrated by the high-performance BOCl/Ca-10 composite, this approach facilitates the design of efficient photocatalysts for the remediation of antibiotic pollutants in water.</p>