The invention relates to potato cake and a preparation method thereof. The potato cake comprises the following materials by weight: 350-450 parts of potato granules, 50-150 parts of potato flour, 400-600 parts of high-gluten flour, 15-18 parts of salt, 16-18 parts of sugar, 10-12 parts of custard powder, 6-9 parts of wheat gluten, 6-8 parts of monosodium glutamate, 5-7 parts of a compound leavening agent, 45-55 parts of edible lard, 40 to 50 parts of edible vegetable oil and 500 to 530 parts of drinking water, wherein the potato granules, the potato flour and the high-gluten flour serve as main materials; the salt, the sugar, the custard powder, the wheat gluten, the monosodium glutamate, the compound leavening agent, the edible lard and the edible vegetable oil serve as auxiliary materials. As both the potato granules and the potato flour are adopted and mixed for preparation of the potato cake, the potato cake is rich and pure in taste; moreover, as the custard powder, the wheat gluten and the compound leavening agent are adopted, the final potato cake can have better taste, and be fragrant, crispy and tasty. The preparation method is simple in process, and suitable for large-scale industrialized production; the finished product of the prepared potato cake is in a frozen state, so that the original taste and nutrition of the food are retained to the most extent, and the potato cake is convenient to preserve, transport and eat.