The clarification of waste sugar solution by α-amylase in the production of preserved sweet potato was studied. Result showed that the optimum α-amylase dosage, temperature, pH value and treating time were 100 U/ml, 55 ℃, 5.5 and 1 h, respectively. The transmittance of clarified sugar solution was over 83%. This study can supply technological support for reusing sugar solution in the production of preserved sweet potato.