The invention provides purple sweet potato cake. The purple sweet potato cake is prepared from the following raw materials: purple sweet potato, glutinous rice flour, millet flour, lucid ganoderma, michelia figo, snowbell-leaf tickelover herb, cherry leaf, hawthorn, purified water, sweetening agent, soybean oil and sesame powder. A processing method of the purple sweet potato comprises the following steps: (1), preparing purple sweet potato pulp for later use; (2), preparing a nutrient solution; (3), preparing mixed liquid; (4), mixing the glutinous rice flour with the millet flour, putting the purple sweet potato pulp, the mixed liquid and the soybean oil into the mixed flour, stirring and mixing, putting the mixture into a mould, and then steaming until the mixture is cooked; (5), rolling the cooked cake in the sesame powder, sterilizing in vacuum and then packing, thereby obtaining a finished product. The purple sweet potato cake utilizes the purple sweet potato as a cake raw material, adds nutrient elements including the lucid ganoderma, the millet flour, the michelia figo and the like, is sweet and delicious, and has healthy functions of increasing appetite, promoting digestion, nourishing the stomach, strengthening the body and the like; the process is simple, the investment is small, the effect is achieved quickly, and standardized production is easy to be achieved.