Abstract: BiOCl is one of the highly promising photocatalysts, but due to its wide bandgap, its solar energy utilization efficiency is low, thereby limiting its photocatalytic performance. In this paper, a series of flower-shaped AgIn₅S₈/BiOCl heterojunction composite catalysts was prepared using a simple solution chemistry method to promote the separation and transfer of photo-generated electrons and holes, effectively extending their light response range into visible light. The photocatalytic degradation effect of the prepared catalysts for tetracycline hydrochloride (TC) under visible light conditions was studied. The optimized sample BOAg-3, prepared with a loading of 0.03 g of AgIn₅S₈, showed a photocatalytic degradation rate of 0.011 9 min^-1 for TC, 2.20 and 1.78 times higher than that of BiOCl and AgIn₅S₈, respectively. The composition, structure, and photoelectrochemical properties of AgIn₅S₈/BiOCl heterojunction photocatalysts were analyzed by various characterization methods (XRD, SEM, PL, etc.), and it is proposed that the separation and transfer of photogenerated electrons and holes at the AgIn₅S₈/BiOCl heterojunction interface is an S-Scheme heterojunction mechanism. In addition, it was found through capture agent experiments that the main active species in the photocatalytic degradation process are superoxide radicals (·O₂^-).