Photocatalysis-Fenton system, based on S-type iron hydroxide oxide/bismuth molybdate supported on biochar, was fabricated for efficient tetracycline removal. Biochar/iron hydroxide oxide/bismuth molybdate catalyst not only exhibits exceptional photocatalytic performance but also accelerates the Fenton reaction cycle in the presence of hydrogen peroxide. Within 40 min, the biochar/iron hydroxide oxide/bismuth molybdate achieved a remarkable degradation efficiency of 97% for tetracycline, surpassing that of biochar/iron hydroxide oxide (65%) and biochar/bismuth molybdate (59%). Experimental analysis and density functional theory calculations confirmed the charge migration mechanism of S-type iron hydroxide oxide/bismuth molybdate. Moreover, the excellent degradation ability of biochar/iron hydroxide oxide/bismuth molybdate was demonstrated across a wide pH range (3–11), overcoming the limitations associated with traditional Fenton systems that operate efficiently only within a narrow pH range. Quenching experiments and electron paramagnetic resonance tests identified primary active species including •O2–, h+, and •OH. Additionally, we elucidated the potential degradation pathway of tetracycline in this study, supplying novel perceptions into synthesizing bifunctional photocatalysts in photocatalysis-Fenton-like systems.