The overuse of antibiotics has led to severe environmental pollution, thereby making it increasingly important to efficiently degrade them. To address this, a unique S-scheme heterojunction of the In 2 S 3 /In 2 O 3 nanocomposite was successfully constructed using hydrothermal coupled with in situ formation in this work. The optimized In 2 S 3 /In 2 O 3 nanocomposite exhibited a significant photocatalytic degradation of tetracycline (TC), achieving an 83% removal rate within 60 min, with enhancements of 1.78 times for In 2 S 3 and 1.66 times for In 2 O 3 . Characterization, experimental results, and density functional theory (DFT) calculation collectively prove the efficient transfer of photoexcited carriers between In 2 O 3 and In 2 S 3 , coupled with the successful construction of the S-scheme heterojunction with a well-arranged band structure. A potential pathway for developing photocatalysts with exceptional antibiotic removal capabilities has been provided by enhancing their reduction and oxidation capabilities of the S-scheme heterojunction through rational structural configuration.