Abstract: To produce sweet potato yoghurt by enzymolysis and fermentation of sweet potato pulp.The sweet potato pulp was hydrolyzed by cellulase andα-amylase to produce the sweet potato pulp.The optimal enzymolysis conditions were determined by single factor and orthogonal experiment.About 42%of juice rate could be obtained at followed conditions:cellulase dosage 0.7%, time 3h, the rate of water and sweet potato pulp 5:1, pH6.5.And then the sweet potato milk was fermented by lactobacillus to produce the sweet potato yoghurt.The optimal fermentation conditions were determined by orthogonal experiment as follows:the proportion of milk powder with sweet potato pulp 5:5, vaccination 5%, fermentation temperature 37℃and the amount of sucrose 4%.The physical, chemical and sensory index of sweet potato yoghurt would be the best at such fermentation process.