The invention discloses a zinc oxide nanocone array with controllable sharpness and a preparation method thereof. The zinc oxide nanocone array comprises a substrate and a zinc oxide nano array arranged on the substrate, wherein the substrate is a conductive substrate; the zinc oxide nano array is a zinc oxide nanocone array, the cone length of the zinc oxide nanocone in the cone array is 0.5-1.5mu m, the maximum cone radius is 100-300nm, and the conicity is 18-40 degrees. The method of the invention adopts the electrochemical deposition method. The method comprises the following steps: firstly adding ammonia water in 0.01-2M of zinc nitrate solution, stirring to ensure that the turbid solution becomes clear, obtaining a zinc nitrate ammino-complex solution, using the conductive substrateas negative electrode to place in 70-100 DEG C of zinc nitrate ammino-complex solution, and electrodepositing for more than 1h under 0.1-5mA of current density to prepare the zinc oxide nanocone array with controllable sharpness. The nanocone array has uniform shape and controllable sharpness; and as the tip of the nanocone is pyramidal, the zinc oxide nanocone array can be widely applied in various fields such as photoelectricity, piezoelectricity, thermoelectric devices and field emission.