A method for generating an electrical stimulation signal applied to electrically stimulate a target zone of an organism by an electrical stimulation device is provided. The electrical stimulation device includes at least an electrical stimulation unit and the electrical stimulation unit includes at least a first electrode and a second electrode. The method comprises the following steps of: receiving a parameter； and delivering a first electrical stimulation signal by the electrical stimulation unit according to the parameter to form an electric field between the first electrode and the second electrode to electrically stimulate the target zone, thereby reducing overactive bladder syndrome. A strength of the electric field covering the target zone ranges from 100 V/m to 1000 V/m. The target zone is a dorsal root ganglion, a spinal cord, a dorsal root, a dorsal horn, a ventral root, or a nerve on a neurotransmission pathway causing the overactive bladder syndrome.
