Statins are widely used in the treatment of hyperlipidemia disease, which are refractory in the municipal sewage treatment plant. The photocatalytic degradation of statins by the Z-scheme heterostructured photocatalyst is confirmed, but the degradation mechanism of statins needs to be further revealed. In this study, the effects of photocatalyst dosage, solution pH and humic acid (HA) on the photocatalysis of fluvastatin by ZnIn₂S₄/Bi₂WO₆ Z-scheme heterostructured photocatalyst (ZIS/BWO photocatalyst) were investigated and the degradation mechanism was proposed. Results showed that adsorption of fluvastatin was improved with the increase of photocatalyst dosage, but photoinduced desorption and light scattering resulted in the decrease of the removal of fluvastatin with high dosage. 0.2$$g/L of the ZIS/BWO photocatalyst was optimal dosage. 65.21% of fluvastatin was removed at pH=9, because high concentration of OH^? was conducive to produce ?OH. The change of pH, competition of photons and active sites, and trapping of reactive oxygen species (ROS) by carboxyl group of HA combined to inhibit the photocatalysis of fluvastatin in the presence of HA. The C–C, C$=$C and C–N bonds of fluvastatin were attacked by a variety of ROS to generate degradable intermediates that were easily mineralized to H₂O and CO₂.