To enhance the photocatalytic performance of bismuth vanadate (BiVO4) and reveal its catalytic mechanism, a multi-walled carbon nanotube photocatalyst (MWCNT/BiVO4) was prepared by sol-gel preparation and an electro-spinning process. Oxytetracycline was used as the target trace persistent pollutant to research its potential degradation pathways catalyzed by MWCNT/BiVO4. X-ray powder diffraction spectroscopy (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM) were used to observe the crystalline phase, morphological structure of MWCNT/BiVO4. The modification by MWCNTs caused changes of functional groups on the surface and a binding energy shift of Bi4f and V2p, as determined from X-ray photoelectron spectroscopy (XPS). Ultraviolet-visible diffuse reflectometry (UV-Vis DRS) revealed that the band gap became narrower and photoluminescence spectra suggested the recombination of photogenerated electron-hole pairs were inhibited after MWCNT modification. All of the characterizations showed enhancement of catalytic performance of MWCNT/BiVO4. The results from the high-performance liquid chromatography (HPLC) indicated that the degradation rate of oxytetracycline had increased by 42.2% and reached 88.7% within 60 min. Electron paramagnetic resonance (EPR) signals of center dot OH and center dot O-2(-) were detected and potential photocatalytic mechanisms of the photocatalysts were put forward. Six reaction pathways were proposed based on ultra-performance liquid chromatography triple-quadrupole tandem mass spectrometry (UPLC-MS/MS) results: demethylation (-14 Da), secondary alcohol oxidation (-2 Da), dehydration (-18 Da), hydroxylation (+16 Da), decarbonylation (-28 Da) and deamination (-15 Da). The present study provides a reference for the application of photocatalytic degradation by MWCNT/BiVO4 on hard degradable substances in aquatic environment.