Aiming at the problems of lower image edge matching, lower peak signal-to-noise ratio(SNR), poor stability and poor enhancement effect of traditional depth image edge enhancement methods, a mismatched edge enhancement method for depth images based on anisotropic diffusion algorithm was proposed. Depth images were obtained by a passive ranging method, image holes were removed by an interpolation algorithm, and the images were filtered according to a weighted median filtering method. Mismatched edges without noise points were detected, and an anisotropic diffusion algorithm was used to fill holes within the mismatched edges. According to the distance from pixel points to holes, an mismatched edge enhancement model was constructed to enhance the mismatched edges of depth images. The results show that the as-proposed method has higher image edge matching, maximum peak signal-to-noise ratio(PSNR), higher stability and optimal enhancement effect, in comparison with three traditional methods.