Pullulanase was used for the enzymatic hydrolysis of potato starch to increase the percentage of the amylose. Response surface methodology based on the Box-Behnken design was employed for the statistical optimization of the medium components for the hydrolysis of potato starch. The combined effects of four independent variables, i.e., the debranching temperature, debranching time, amount of pullulanase and pH were analyzed using a reduced cubic model, which was developed by Box-Behnken design in predicting the optimum debranching degree of potato starch. Under these conditions, the model predicted the best debranching environments: debranching temperature 52.79 A degrees C, debranching time 2.09 h, amount of pullulanase 58.16 U/g and pH 4.18. The differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA) and Infrared spectrometer were used to evaluate the thermal properties, the structure of the native and debranching potato starch (DPS) so as to support the corresponding variation in the DPS. The debranching increased the onset temperature, peak temperature and end temperature of native potato starch, but decreased its melting enthalpy. The absorption peak intensity of the OH groups at wave number 3400 cm(-1) in IR spectra was obviously strengthened after the native potato starch was debranched. It indicated that the amylose content in DPS was increased.