The present invention discloses a fusion channel based and sky immune image defogging method, relates to the technical field of digital image processing, and solves problems that in the existing image defogging method, after defogging, the defogging effect is poor due to color distortion in the sky area, and occurrence of the phenomenon of halo and the block effect, and the existing method has a cumbersome recognition process, a large amount of calculation, and so on. The method disclosed by the present invention comprises: carrying out minimum and maximum values filtering on a fog image, roughly estimating atmospheric light, introducing correction factors, and carrying out rough estimate on the transmittance of the dark channel and the transmittance of the bright channel respectively; using the guided filter to carry out precise optimization respectively, determining whether the transmittance of the dark channel is greater than the transmittance of the bright channel (wherein, if so, the dark primary channel image is the sky area, and if not, the dark primary channel image is not the sky area), and obtaining precise estimate of the fusion transmittance; and taking the pixel mean value as the adaptive accurate estimate and the fusion transmittance of the atmospheric light, and obtaining a clear defogging image by using the atmospheric scattering imaging model.