To optimize the preparation process of non-crystalline maize starch and characterize its structure,the refrigerated planetary ball mill was employed to produce non-crystalline maize starch and the technical conditions of the ball mill were optimized using response surface test.Based on the single-factor test,the mathematical regression model was established through Box-Benhnken center composite design and response surface analysis.Then the optimum technical conditions are achieved as the milling time of 2.35 h,the rotating speed of 482 r/min and the ratio of ball to material of 5.68:1.Under these conditions,the relative crystallinity of non-crystalline maize starch reaches 1.91%.No new functional group is found in the non-crystalline maize starch by the analysis of FT-IR spectrogram.The characteristic absorption band of 1 047 cm-1 characterizing the crystalline structure of non-crystalline starch disappears,and that of 1 018 cm-1 characterizing the amorphous structure of the starch is broadened.13C CP/MAS NMR analysis indicates that the regular double helix structure in native maize starch has been uncoiled to the disordered single helix structure in non-crystalline maize starch.