Abstract: Drying characteristics of purple sweet potato under infrared and the mathematical model were studied.The experimental data were collected of the changes of the moisture ratio( MR) of purple sweet potato slices with the drying time( t) with different slice thicknesses and drying temperatures,and the drying curves of the purple sweet potato slices was graphed accordingly. The results showed that the slice thicknesses and drying temperatures had significant influences on the drying characteristics of purple sweet potato under infrared: higher drying temperatures and thinner slice thicknesses lead to higher water loss rate( WLR) and shorter drying time.Also,the fitting calculation showed that the forecast value of Page Model of the three basic drying models was fit with the actual value and could better reflect the drying process. The coefficients in Page Model were then calculated,and the mathematical model of the drying of purple sweet potato was determined as: MR = exp(- kt~n),k = exp(- 6.597951 + 0.034936T- 0.305989L),n = 1.218926,MR = moisture ratio,T = drying temperature( ℃),L =purple sweet potato slice thickness( mm).