The invention relates to a low-sugar low-fat cassava mooncake and a preparation method thereof. The low-sugar low-fat cassava mooncake is prepared from the following raw materials in parts by weight: 70 to 120 parts of cassava starch, 40 to 90 parts of corn starch, 30 to 85 parts of oat powder, 25 to 50 parts of Chinese yam powder, 40 to 60 parts of small red beans, 35 to 60 parts of mung beans, 30 to 55 parts of coix seeds, 20 to 50 parts of green tea, 15 to 35 parts of wolfberry fruit, 35 to 65 parts of Chinese chestnuts, 5 to 20 parts of shaddock peel, 30 to 50 parts of roasted pork, 1 to 15 parts of sunflower seed oil, 45 to 80 parts of black sesame, 60 to 90 parts of nut kernels and 5 to 20 parts of honey. The invention also provides the preparation method of the low-sugar low-fat cassava mooncake. The low-sugar low-fat cassava mooncake provided by the invention has natural color and luster, clear texture, smooth, soft and non-greasy taste and rich nutrition, is sweet and delicious, has low-sugar, low-fat and low-heat health-care effects, and is suitable for everyone to eat.