Porous ZnO nanowire (NW) arrays were synthesized by a one-pot ammonium hydroxide-assisted hydrothermal method. By controlling the volume proportion between the solution and the bottle, ZnO NW arrays as long as 20μm have been obtained in a short duration of 8h, indicating a high growth rate of 2.5μmh−1. Further prolonging the hydrothermal reaction time to 20h, ZnO NWs become porous, which is a key advantageous feature for ZnO NW arrays based dye-sensitized solar cells (DSSCs). By TiO2 coating and N-719 sensitizing, the power conversion efficiency of the porous ZnO NW–TiO2 based DSSC reaches 3.06%.