The invention provides an automatic white balance correcting method which includes the steps of collecting reference white points of an image to be corrected, determining the reference white points to draw a reference white region, calculating the number of the reference white points, currently located in the reference white region, of the image to be corrected, judging whether mixed color temperature exists in the image to be corrected or not, if the number of the reference white points is smaller than or equal to a first preset threshold value or it is judged that the mixed color temperature exists in the image to be corrected, calculating white balance gains through a preset algorithm strategy, carrying out color complementing correcting on the image to be corrected through the white balance gains, if it is judged that the mixed color temperature does not exist or the number of the reference white points is larger than the first preset threshold value, calculating the white balance gains according to the number of the white points located in the reference white region, and carrying out color complementing correcting on the image to be corrected through the white balance gains. According to the automatic white balance correcting method, the color shifting problem generated when the image is corrected through the white balance gains calculated with a reference white region table look-up method when the number of the reference white points is excessively small and the mixed color temperature exists is solved.