In this paper, ultra-thin nanofiber PDI was obtained by self-assembly dispersion of commercial PDINH. A novel Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material was constructed by a simple solvothermal method. XRD, SEM, TEM, FT-IR and other characterization techniques proved the successful preparation of the Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material. By degrading chlortetracycline hydrochloride, it was found that the photocatalytic activity of Co/Ni-MOF-74@PDI was much higher than that of pure Co/Ni-MOF-74 and PDI. Subsequently, Co/Ni-MOF-74@PDI was used to activate H 2 O 2 to further improve the degradation efficiency of chlortetracycline hydrochloride. It was found that the photocatalytic performance was greatly improved after the addition of 19.6 mM H 2 O 2 to the system, and the degradation rate of chlortetracycline hydrochloride was 87% within 90 min. The electron transfer pathway and H 2 O 2 activation mechanism of the Co/Ni-MOF-74@PDI composite photocatalyst were proved by free radical quenching experiments, electron paramagnetic resonance analysis and X-ray electron spectroscopy. Finally, the easy exfoliation point and degradation pathway of chlortetracycline hydrochloride were studied using density functional theory, UPLC-MS and toxicity evaluation software. It was found that the main active substances were h + , ˙O 2 , 1 O 2 and ˙OH, and the toxicity of chlortetracycline hydrochloride and its intermediates was evaluated.