Currently, upconversion nanoparticles (UCNPs) based photocatalysts have been extensively developed to improve solar energy utilization. However, the mechanisms underlying interfacial energy migration of upconversion photocatalyst remain unclear. Herein, a promising composite photocatalyst with complementary properties is designed by integrating β-NaGdF4:Yb3+/Er3+ (NGFYE), CdS and multi-walled carbon nanotubes (MWCNTs). The morphology, structure and chemical properties of NGFYE@CdS/MWCNTs ternary photocatalyst are characterized. In addition, the existence of Förster resonance energy transfer process in NGFYE@CdS/MWCNTs photocatalysts, i.e., the migration of excitation energy from Er3+−4S3/2 excitation level and higher excitation level (e.g., Er3+−2H11/2) to CdS nanoparticles, was further confirmed by density functional theory (DFT) calculations. The optimized NGFYE@CdS/MWCNTs photocatalyst presents 71.65 % and 35.29 % degradation of tetracycline hydrochloride (TCH) and ciprofloxacin (CIP) under λ ≥ 800 nm irradiation for 3 h, respectively. This work not only illustrates the interfacial energy migration mechanism between NGFYE and CdS, but also provides insights for the rapid construction of heterojunction materials with efficient energy transfer interfaces.