In the clean production process of sweet potato starch, sweet potato juice was obtained from fresh sweet potato extrusion without adding any water to avoid producing a great deal waste water.A large amount of soluble protein and sugar were dissolved in the potato juice and therefore reduced its content in the potato residue.Thus, avoiding the high concentration of COD in the wastewater and reduced wastewater treatment.The clean production was divided into two parts: sweet potato pretreatment and starch extraction.The pretreatment experiment of sweet potato showed that the starch dissociation rate was 92.33%, protein content and sugar content in the potato residue were reduced by 54.16% and 98.09% respectively.The above results were obtained at the conditions of gel grinding interval of 5.0 μm and the ratio of sweet potato and liquid 1∶0.3, with twice residue separation.The extraction process of starch includes two parts- from the potato juice and potato residue.The results of starch extraction test in sweet potato residue showed that the extraction rate of starch could be increased by ultrasonic at power of 300 W and extracting 5 min.Through single factor test and response surface optimization, the best conclusions were: the ratio of water to solid 1∶4.9, pH 8.0, 30 ℃, extracting for 1h.Under the above conditions, the starch extraction rate was as high as 90.91%, starch wastewater is 158 mL/100g, chemical oxygen demand (COD) was 3 600 mg/L, suspended solids (SS) was 510 mg/L, the chroma was as high as 60 times.