The invention discloses a security alert method and system in an external auditory masking state. The method comprises the following steps: A, collecting external audio information of an environment where a mobile device is located currently; B, carrying out match in a vehicle audio matching database according to the external audio information to obtain a corresponding vehicle model number, and carrying out detection according to the vehicle model number and the external audio information to obtain an impatience degree and a strength value; C, carrying out match in a matching rule database of audio perceptual intensity and distance values by using parameters of the vehicle model number, the impatience degree and the strength value to obtain a danger level; and D, providing corresponding security alert for a user according to the danger level.