Abstract <p>Photocatalytic technology, renowned for its green, economical, and highly efficient characteristics, has garnered significant attention in the fields of wastewater treatment and environmental remediation. In this study, Ba_0.7Sr_0.3TiO₃ was synthesized via the solid-state method, and g-C₃N₄ was incorporated to construct a g-C₃N₄/Ba_0.7Sr_0.3TiO₃ multiphase composite with enhanced photocatalytic performance. The photocatalytic efficiency of the composite catalysts with varying mass fractions was evaluated for the degradation of tetracycline hydrochloride. The g-C₃N₄/Ba_0.7Sr_0.3TiO₃ composite was characterized using XRD, SEM, UV–Vis, and PL techniques to analyze its crystal structure, microstructure, and optical properties. The results demonstrated that the composite with 5% g-C₃N₄ mass fraction exhibited the highest photocatalytic activity, achieving a tetracycline hydrochloride degradation rate of 86% within 120 min, compared to 67% for pure Ba_0.7Sr_0.3TiO₃. These findings indicate that the incorporation of g-C₃N₄ effectively reduces the band gap of the composite, increases carrier concentration, and significantly enhances photocatalytic performance. This study highlights the potential of g-C₃N₄/Ba_0.7Sr_0.3TiO₃ as a promising material for photocatalytic applications in environmental remediation.</p>