ZnWO4 photocatalysts with various morphologies were synthesized by a hydrothermal process. The effects of hydrothermal temperature and time on the crystallinity and morphology of ZnVVO4 catalyst were investigated. The crystallinity was enhanced with the increase of hydrothermal temperature and hydrothermal time. The formation of ZnWO4 nanoparticles was controlled via kinetic process above 160 degrees C, and ZnWO4 nanorods with a highly [100]preferred orientation formed via the thermodynamically control process in the temperature range of 120-140 degrees C. The morphology and crystallinity of ZnWO4 photocatalyst have a significant influence on the photocatalytic activity for aqueous Rhodamine B and gaseous formaldehyde degradation. ZnWO4 nanorod catalyst showed a much higher photocatalytic activity than the nanoparticle one. The enhanced photocatalytic activity can be attributed to the anisotropic structure of nanorod.