The invention relates to a donkey-hide gelatin cake with the effects of mildly nourishing and a preparation method thereof. The donkey-hide gelatin cake comprises the following raw materials in parts by weight: 50-150 parts of donkey-hide gelatin, 50-150 parts of oxhide gelatin, 100-300 parts of black sesame, 80-200 parts of watermelon seed kernels, 50-150 parts of sunflower seed kernel, 1-25 parts of American ginseng, 200-400 parts of yellow wine and 40-120 parts of xylitol. The donkey-hide gelatin cake and the preparation method have the advantages that the donkey-hide gelatin is used as the raw material, and the oxhide gelatin with the milder nourishing effect is used for replacing partial donkey-hide gelatin; moreover, since the watermelon seed kernels, the sunflower seed kernels, the American ginseng and the xylitol with mild nature are added as the auxiliary materials, the nourishing effect is milder than that of the traditional donkey-hide gelatin; not only are the effects of nourishing and replenishing blood, replenishing and tonifying qi and nourishing Yin and moistening dryness achieved, but also symptoms such as internal-heat increase caused by the donkey-hide gelatin cake can be prevented, tonifying without dryness is achieved and the effects of clearing heat and increasing fluid and relaxing bowel can be achieved.