The invention discloses a method for removing black noise in an image. The method comprises the following steps that: according to the color value of an image to be processed, generating a dark channel map and a bright channel map of the image to be processed; carrying out fusion on the dark channel map and the bright channel map to generate a fused image; according to the gradient direction of each pixel in the fused image, carrying out calculation to obtain a new fused image; calculating the gradient map of the new fused image; and taking the gradient map as an orientation map, and carrying out oriented filtering on the image to be processed to obtain an image of which the black noise is removed. According to the scheme of the method, on the basis of the dark channel and the bright channel of the image, the orientation map is constructed, and a black noise area can be clearly filtered while an image edge is kept. The invention also discloses a computation device used for executing the method.