The invention discloses a denoising method and device for a quantum dot fluorescence image on the surface of a porous silicon biosensor, and the method comprises the steps: analyzing the noise type in the quantum dot fluorescence image, and determining the noise type as gamma multiplicative noise; performing non-local mean smoothing processing on the obtained quantum dot fluorescence image, and taking the filtered image as a reference standard image for gray compression; obtaining a plurality of homogeneous regions of the noisy fluorescence image, averaging the variation coefficients of each homogeneous region to obtain an estimated variation coefficient, and determining the number of gray compression iterations; performing gray compression preprocessing on the noisy fluorescence image, taking the ratio of the smoothed image to the original fluorescence image as a compression coefficient, and performing compression according to the number of iterations; adopting a non-local anisotropic diffusion method, calculating the non-local cosine distance of each pixel point to obtain a threshold value of a diffusion coefficient, solving a differential equation to remove noisy points, and recovering an original gray value. The device comprises an analysis module, a smoothing module, an acquisition module, a compression module and a recovery module.