A searching method for finding a target location in a variable space is provided. The variable space is constructed by a set of variables and has multiple sub-spaces. The target location renders an output result of a wireless communication system to satisfy a target value. The search method includes steps of: providing the set of variables; identifying a target sub-space where the target location is located from the sub-spaces; obtaining a plurality of gradients of the output result at a predetermined location from the target sub-space, each of the gradients corresponding to a direction of change; and selecting one from the directions of change according to the gradients, and changing values of the set of variables according to the selected direction of change to find the target location.