Abstract: The invention discloses an air outlet protection structure, an outdoor unit of an air conditioner and a method for designing an air outlet protection structure. The air outlet protection structure comprises: a central circular disk (10); and a radiating rib (20), extending from an outer edge of the central circular disk (10) to a direction away from the central circular disk (10). An included angle between a first side surface (21) of the radiating rib (20) and a central axis of the central circular disk (10) is a, as formula (I). The invention is determined according to the characteristics of a flow field of an air duct, and can reduce the hindering effect of an air outlet protection apparatus on a fluid as far as possible, thereby improving the air output volume of a fan and reducing the noise of the entire outdoor unit of the air conditioner.