Photoanodes in quantum-dot-sensitized solar cells are essential to the process of light collection and charge transfer. In this paper, three-dimensional inverse opal (ZnO@ZIF-8 3D IO) photoanode is fabricated via a self-assembled opal template method. The synthesized photoanode has completely connected pores with extended diameter, thus promoting the permeability of QDs and electrolyte. Meanwhile, the light trapping ability and charge transfer process can be enhanced due to the slow photon and multi-scattering effect of the regularly interconnected macroporous array structure. ZIF-8 shell coated on the surface of ZnO IO not only provides high porosity but also serves as a protective passivation layer to reduce the carriers recombination occurred at the interfacial. In order to investigate the charge transport mechanism of ZnO @ ZIF-8 IO, cascaded CdS/CdSe quantum dots were used as sensitizers. Benefiting from the IO structure and ZIF-8 modification, the photoelectric conversion efficiency of solar cells based on ZnO@ZIF-8 IO can reach 1.75% (1.71 +/- 0.04%), almost twice of that of the solar cells based on ZnO IO photoanode (0.81 +/- 0.05%).