Fluvastatin, a commonly used cholesterol-lowering drug, has attracted considerable attention because of its adverse effects on human beings. Photolysis and ZnIn2S4 photocatalysis of fluvastatin under UV-Vis irradiation were compared based on analysis of reactive oxygen species (ROS), degradation pathways, and toxicity evaluation. The removal rates of fluvastatin by photolysis and photocatalysis were 71.07% and 99.79%, respectively. Photolytic degradation of fluvastatin was conducted in the absence of ROS, whereas center dot O-2(-) played a vital role and center dot OH played an auxiliary role during the photocatalytic process. The photolytic degradation of fluvastatin was achieved through cleavage of the C-C, C-N, and C=C bonds. Because of the limited photon energy, photolytic products with stable structure did not decompose easily, which resulted in chemical oxygen demand (COD) removal rate of the photolytic system only 15.62%. The photocatalytic degradation of fluvastatin was achieved through direct cleavage of the chemical bonds under the synergistic oxidation of center dot O-2(-) and center dot OH, and the hydroxylation reaction under center dot OH attack. The COD removal rate of the photocatalytic system reached 43.05%. The photocatalytic samples were slightly less toxic than fluvastatin, whereas the photolytic samples were more toxic than fluvastatin. Therefore, the toxicity of the photolytic samples was significantly higher than that of the photocatalytic samples. Photocatalysis was an effective way for mitigation and elimination of harm of statins to the environment than photolysis.