Abstract: Formula and fermentation technology of yogurt with purple sweet potato was studied. The optimal formula and fermentation technology which were ascertained by orthogonal experiments that was as follows:purple sweet syrup 6%, white sugar 7%, compound stabilizing agent with 0.1% CMC and 0.1% sodium alginate, inoculum 4%, fermentation temperature 41℃, fermentation time 5h.The test was not only enriching the varieties of yogurt, but also improving the nutritional value of yogurt.