Melem/g-C₃N₄/vermiculite hybrid photocatalyst (CNV-X) with a sandwich structure for degrading tetracycline was constructed by hydrothermally treating the pre-synthesized g-C₃N₄/vermiculite composite (CNV). With the enhancement of hydrothermal temperature, part of g-C₃N₄ was gradually transformed into thorn-ball-like melem, the specific surface area of the samples increased step by step from 9.88 m²/g for CNV to 33.93 m²/g for the sample hydrothermally treated at 180 °C (CNV-180). Then, the specific surface area of CNV-X dramatically decreased to 6.36 m²/g when hydrothermally treated at 200 °C. The variation trend of photocatalytic performance of CNV-X samples with the hydrothermal temperature was similar to that of specific surface area. CNV-180 exhibited the optimum photocatalytic performance, it (0.05 g) degraded 81.82% of tetracycline molecules (100 ml, 20 mg/L) after photocatalysis for 120 min, and the reaction rate constant (0.0137 min⁻¹) was 2.74× that of pure g-C₃N₄. CNV-180 exhibited excellent stability and reusability which degraded 77.68% of tetracycline molecules after five 120-min cycles. The degradation rate of the melem/g-C₃N₄/vermiculite composite with respect to tetracycline was 77.68% after five 120-min cycles. The significant improved photocatalytic activity was due to the enhanced specific surface area, the enhanced optical absorption property, prohibited recombination, and accelerated separation and transfer efficiency of photo-generated electron-hole pairs, which can be ascribed to the sandwich structure, the heterojunction of g-C₃N₄/melem, and the electrostatic repulsion between photo-generated electrons and the permanent negative charges of the vermiculite layers. Moreover, the band structure, the main active substance (·O₂⁻), and a photocatalytic mechanism were proposed. Thus, this study provided a promising approach to photo-degradation of tetracycline and potential applications to vermiculite-based photocatalytic materials.