In this study, a long ZnO nanowire (NW) array was synthesized using a continuous flow injection (CFI) process to replace the conventional multi-batch process. According to electrochemical impedance spectroscopy (EIS) measurements, the diffusion coefficient of the ZnO NW array by a CFI process is higher than that of ZnO NWs using a multi-batch process. In addition, the electron transit time was found to depend on the thickness of the ZnO NW array. To effectively improve the conversion efficiency of ZnO NW dye-sensitized solar cells (DSSCs), a high diffusion coefficient of the ZnO NW array with 1.2 × 10⁻² cm² s⁻¹ was synthesized by an ammonia-assisted CFI process. In addition, ZnO NPs were covered along the ZnO NW array as a ZnO NW/NP photoanode to provide a high dye adsorption area for increasing electron injection flux. In this study, the growth period of ZnO NPs playing a crucial role in the electron transport of the ZnO NW/NP photoanode was demonstrated. A high-efficiency DSSC of 6.8% is achieved using a N719-sensitized ZnO NW/NP photoanode with 25 μm.