Abstract: Starch is a kind of natural macromolecular compound. It is widely used in food processing, paper making, medicine and other fields because of its advantages such as low price, renewable and biodegradable. However, natural starch has many deficiencies in nature, so it is usually modified appropriately to be applied widely. In this study, ball-milling method was used to modify wheat starch to explore the effect of ball-milling time on the physicochemical and structural properties of wheat starch, to provide a theoretical basis for further research on the effect of ball-milling treatment on the functional properties of wheat starch, and to provide technical support for the expanded application of wheat starch. Planetary ball-milling was used to treat wheat starch (made by martin method) for 1 h, 2 h, 3 h and 5 h respectively, and the rotate speed was 200 r/min. Laser particle size analyzer, scanning electron microscope (SEM), polarizing microscope (PLM), X-ray diffractometer (XRD), rapid viscosity analyzer (RVA) and differential scanning calorimeter (DSC) were used to characterize the particle size distribution, particle apparent morphology, polarized cross, gelatinization and thermal properties of wheat starch, respectively. The results showed that the starch grain size decreased significantly with the increase of milling time and the D₁₀, D₅₀, D₉₀ and S of starch granule decreased from 9.83 μm, 17.82 μm, 51.33 μm, 2.33 μm, to 5.42 μm, 13.79 μm, 21.71 μm, 1.19 μm after 5 h treatment, respectively. The curve of particle size distribution showed that with the increase of milling time, the curve moved to the range of small particle size. The SEM images showed that the longer the ball-milling time, the greater the degree of starch granule ruptured and the granule surface gradually became rough. PLM images showed that when the milling time was prolonged, the polarization cross of starch particles gradually disappeared. XRD results showed that the crystallinity of starch was reduced from 20.00% to 16.78%, indicating that the starch crystallization area was destroyed. In addition, the gelatinization properties of wheat starch, such as peak viscosity, trough viscosity, breakdown and final viscosity were reduced by ball-milling. This was because the side chain of amylopectin was broken under mechanical force after ball-milling, resulting in an increase of low molecular weight starch content and a higher gelatinization of starch. The gelatinization enthalpy ΔH was also significantly reduced, which was attributed to the decreased absorbed heat by hydrogen bond breaking in the partially broken chemical bonds under mechanical force. In a word, the gelatinization and thermal properties of starch granules were changed due to the destruction of starch granule structure and crystalline structure.