A fast scan detection method is provided. The fast scan detection method is applied to a rotatable scan detection device where two or more detection samplings are performed for calculating each scan detection distance value, where each of the detection samplings includes: emitting, by an emission light source, infrared detection light, where the infrared detection light propagates through a surrounding space and is reflected by a detected object when the infrared detection light encounters the detected object; and receiving, by a photoelectric sensor in a reception unit, the infrared detection light reflected by the detected object, where the rotatable scan detection device performs one detection sampling at each detection angular position at which the rotatable scan detection device is positioned.