Conjugated polymer P3HT coupled with hierarchical ZnO (H-ZnO) photocatalysts were fabricated by a two-step solution method with assembling P3HT nanoparticles on the surface of H-ZnO micro-flowers. Optical properties revealed that the fabricated H-ZnO micro-flowers were rich in defects. The as-prepared P3HT@H-ZnO composite exhibited higher photocatalytic activity than H-ZnO for photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The enhanced photocatalytic activity was attributed to the strengthened visible light absorption and the closely contacted interface between P3HT and H-ZnO. Based on the reactive species trapping experiments and band gap structure analysis, it can be identified that the effective separation and transfer of the photo-induced electron-hole pairs within the P3HT@H-ZnO composite follow a Z-scheme mechanism rather than type II heterojunction. The present work will provide a new insight to design Z-scheme photocatalysts with enhanced photocatalytic performance via metal-free polymers modification.