The invention discloses a high-fat low-sugar moon cake and a preparation method thereof. The technical problem of decreasing the sugar content of moon cakes is solved. The high-fat low-sugar moon cakeis prepared from the components in percentage by mass: 66% of moon cake skin and 34% of fillings, and the mass ratio of fat to protein to sugar is (1.0-10) to (1-0) to 1. The preparation method of the high-fat low-sugar moon cake includes the following steps that the moon cake skin is prepared, the fillings are prepared, and the high-fat low-sugar moon cake is prepared. According to the high-fatlow-sugar moon cake, compared with the prior art, the sugar content of the moon cake is decreased, and the moon cake accords with the ketogenic diet high-fat low-sugar ratio structure, is rich in dietary fibers, low in calorie per unit, good in taste, high in fat and not greasy, can be used as diet therapy food of patients of epilepsy, diabetes, tumors, behavioral abnormalities, autism, spinal cord injury, weight loss, fat reduction, alzheimer disease and parkinson disease, and is suitable for eating of the general population.