Abstract: Abstract: Jet-milling is one of the effective techniques that can alter structure and properties of starch. In this research, the effect of modification in terms of molecular structure and its physicochemical properties of maize starch was studied by scanning electron microscopy (SEM), laser particle size analyzer (LPA), X-ray diffractometry (XRD), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), rapid visco analyzer (RVA). The properties of starch solubility, swelling power, water binding capacity, freeze-thaw stability, were also studied. The results show that the shape of maize starch granule changed from native polyhedron to anomalistic state through the jet-milling superfine grinding processing. The starch granules were crashed into tiny particles and even part of them fracted. The distribution of starch granules became more concentrated. The distribution of raw maize granules concentrated from 10 μm to 20 μm before the milling, whose median diameter was 14.37 μm. The distribution of micronized maize granules concentrated from 1 μm to 10 μm, and the median diameter decreased to 5.25 μm. Meanwhile, the polarization cross of micronized maize starch graule reduced gradually. Through the jet-milling superfine grinding processing, the feature of peak diffraction in the diffractogram gradually weakened, including the widened half peak width and decreased peak intensity. The micronized starch showed A-type pattern, which displayed the diffraction peak on diffraction angle 2θ at 15°, 17°, 18° and 23°. The crystal structure was destroyed and the crystallinity decreased from polycrystalline to amorphous state while jet-milling, with relative crystallinity decreasing from 33.43 % to 15.46 %. Through the jet-milling superfine grinding processing, the feature of infrared spectroscopy showed no new characteristic absorption peaks. Vibration band narrowed down and strengthened at 3 422 and 2 930 cm-1, while weakened at 1 082 cm-1 and 992 cm-1. Meanwhile, the enthalpy and peak temperature changed after the milling. The pasting temperature of micronized maize starch decreased, including initial temperature, peak temperature and final temperature. Enthalpy also decreased from 22.25 to 14.29 J/g. All that made the significant influence of thermodynamic property of micronized starch. The viscosity of micronized maize starch also decreased, including peak viscosity, final viscosity, breakdown viscosity and set back viscosity. Degree of decay and retrogradation value of micronized maize starch were below 2.5 times and 1.47 times respectively for the native maize starch. The solubility and the swelling power of the samples showed a significant increase at the same measuring temperature, and the solubility and swelling power also increased with increasing temperature at the same superfine milling time. Furthermore, the water binding capacity and freeze-thaw stability of the micronized starch changed for the better than the untreated. The results shows that the jet-milling can change microstructure, physical and chemical properties of maize starch. The effect of jet-milling of maize starch exhibited a better both hot stability and cool stability of paste. It is not a simple physical modification method for starch to be processed by superfine grinding with jet-milling. It is a homeostasis process that changes the complex energy conversion and starch properties. This study provides a theoretical basis and technical support for improving deep exploitation and utilization of maize starch, respectively.