A defogged image denoising method based on transmissivity comprises the steps: (1) obtaining a defogged image containing noise and a transmissivity image, (2) roughly estimating an overall noise variance, (3) according to the noise variance confirmed in the step (2), confirming and calculating several parameters, (4) according to the parameters, searching similar pixels, using the transmissivity as a criterion, pre-screening the pixels in the searching range, and removing points dissimilar to pixels to be denoised, (5) constructing a correction factor based on the transmissivity and weakening pixel weight polluted by the noise, (6) calculating a gradient mean value difference of a whole image and a searching window, inputting a built parameter optimization model, and conducting adaptive correction on denoising parameters in different areas, (7) calculating a similarity weighted mean value of all the pixels in the searching range to replace the pixels to be denoised, and (8) outputting a denoising result after all the pixels are processed. The defogged image denoising method has the advantages of being high in detail protection degree, good in denoising effect, low in complexity and the like.