Abstract: Abstract: Starch, as one of the most abundant natural polymers, is available, sustainable and non-toxic. However, it has not exhibited great development potential and application prospect in the food processing fields due to the low transparency and solubility. Mechanochemistry is the treatment process of converting the mechanical energy, such as grinding, shearing, pressure and friction, into chemical energy, during which the structure and properties of materials are changed. In order to improve the properties of starch and expand its application fields, corn starch was processed by high pressure homogenization. High pressure homogenization could produce strong shearing, vibration, cavitation effects, and so on, which was a complex process that could change the structure and properties of materials. In this research, corn starch was used as raw material, and was processed at the homogenizing pressures of 20, 60, 100 and 140 MPa successively to analyze the changes of microstructure and physicochemical properties. The mechanochemical effects of homogenizing pressure on corn starch were revealed. In this study, the structure and properties of corn starch modified by different homogenizing pressures, such as crystallinity and morphology structure, were analyzed by X-ray diffraction (XRD), polarizing microscope (PLM), scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM). The physicochemical properties of starch, including solubility, swelling power, transmittance, gelatinization properties and thermal characteristics, were studied by rapid visco analyzer (RVA) and differential scanning calorimetry (DSC), and so on. And the relationships and mechanisms between structure and properties were revealed. The results showed that compared with native corn starch, the granule appearance of modified starch had changed. There occurred the spherical structure with the increase of the pressure from 20 to 100 MPa, and this phenomenon was the most pronounced when the homogenizing pressure was 100 MPa. The XRD showed that corn starch had an A type pattern with sharp peaks of 15.3°, 17.1°, 18.2° and 23.5°, respectively. And the type of corn starch modified by different homogenizing pressures was not changed. However, the crystallinity decreased after homogenization treatment. When the homogenizing pressure was 140 MPa, the results from PLM showed the crystalline structure of corn starch was damaged. The results demonstrated that crystalline regions of starch granule were destroyed at the pressure of 140 MPa. In addition, as the homogenizing pressure increased from 20 to 140 MPa, the average particle sizes of corn starch granules decreased. And it revealed that high pressure homogenization had reduced the particle sizes of starch through cavitation and shearing. Meanwhile, the properties of gelatinization weakened gradually, including the peak intensity, low viscosity, final viscosity and gelatinization temperature. Whereas, with the increasing of homogenizing pressure, the solubility and transmittance of corn starch modified by different homogenizing pressures showed a significant increase. To sum up, the present results reveal that the influence of high pressure homogenization on the structure and properties of corn starch is obvious. And different homogenizing pressures have different mechanochemical effects on the amorphous, sub-crystalline regions and crystalline regions of starch granule, and typical aggregation and agglomeration effects occur successively in starch granules.