Bifunctional photocatalysts, namely, magnetic TiO2 composites (TiO2/SiO2/Fe3O4, TSM), were prepared and used to degrade dimethyl phthalate (DMP), which is suspected of having endocrine-disrupting effects and a high potential to threaten aquatic environments. The main factor affecting the deposition of titania on the magnetic carrier (SiO2/Fe3O4) for the preparation of TSM composites investigated in this study was the water-to-titanium ratio (WTR) in the range of 60-250. The TSM composites were characterized by SQUID, TEM, XPS, XRD, UV absorption, and zeta potential analysis. The effects of the dosage of TSM composite and solution pH on the photodegradation of DMP were also investigated. The best water-to-titanium ratio for the synthesis of the thickest film of TiO2 on the magnetic carrier in a homogeneous nucleation system was determined to be WTR = 130. The obtained TSM composites were superparamagnetic and mainly exhibited the crystalline structure of the anatase phase. The energy gap and pH(PZC) of TSM130 were found to be 3.2 eV and 5.6, respectively. The degradation of DMP using TSM composites was found to follow pseudo-first-order kinetics, and the calculated values of the rate constant were in the range of 0.0014-0.0037 min(-1). Furthermore, the adsorption and the photodegradation efficiency of DMP were significantly affected by the solution pH value. A 1.2 g L-1 dosage of TSM130 in the photocatalytic system was found to ensure the most effective utilization and minimal detrimental scattering of radiation. The results led to the conclusion that TSM composites, which can be easily separated from solution by magnetic field, exhibit good photocatalytic activity in the degradation of DMP.