Hierarchical zinc oxide (ZnO) quasi-spheres consisting of nanoparticles with diameter of about 20 nm were synthesized via a one-pot reaction. The size of ZnO quasi-spheres is easily tunable from 80 nm to 3 μm by varying the type of zinc source and its concentration. The three samples 1-3 with the diameter of 80-180 nm, 300-600 nm and 1.2-2.9 μm were selected for fabricating dyesensitized solar cells (DSSCs) and their photovoltaic properties were measured. The results demonstrate that DSSCs fabricated by sample 2 with the diameter within the wavelength of visible light obtain the highest short-circuit current density and over light conversion efficiency, due to resonant scattering increasing the photon absorption.