The photocatalyst ZnFe2O4 (ZFO) nanoparticles with different diameters were synthesized by a solvothermal method using water, ethylene glycol (EG) and methylgiycol (EM) as the solvents. The results showed that the polarity of the solvents has an important influence on morphology and photocatalytic performance of the ZnFe2O4. The higher polarity of the solvent (H2O) was benefited to form smaller diameter nanoparticles, which showed higher photocatalytic efficiency. The removal efficiencies of the ZFO/H2O, ZFO/EG and ZFO/EM for MB were 85.42%, 61.11% and 51.19%, which accorded with the order of the polarity of solvents.