In this work, a GaOOH/ZnBiTaO₅ heterojunction photocatalyst was synthesized innovatively and characterization techniques including XRD, SEM-EDS, XPS, FT-IR, PL and UV-Vis DRS were carried out to analyse the structural and morphological properties of the GaOOH/ZnBiTaO₅ heterojunction photocatalyst. The GaOOH is dispersed on the surface of ZnBiTaO₅ to form a heterojunction structure according to the SEM image. The band gaps of 10 wt%, 25 wt% and 50 wt% GaOOH/ZnBiTaO₅ heterojunction photocatalysts were calculated to be 3.21 eV, 3.22 eV and 3.23 eV, respectively, which were between the band gaps of pure ZnBiTaO₅ (3.19 eV) and pure GaOOH (4.76 eV). The photocatalytic performance of the GaOOH/ZnBiTaO₅ heterojunction photocatalyst was investigated by degrading enrofloxacin under ultraviolet light. The results showed that the as-prepared 25 wt% GaOOH/ZnBiTaO₅ presented optimal photocatalytic performance and could remove 58.27% of enrofloxacin in 60 min, which was higher than that of pure ZnBiTaO₅ (53.7%) and pure GaOOH (35.4%). In addition, it was confirmed that ˙O₂⁻, h⁺ and ˙OH were all the active radicals during the degradation process. Finally, the possible degradation mechanism of enrofloxacin was discussed in detail. This work provided a viable strategy for improving the photocatalytic performance of wide band gap semiconductors.