Using Bainong 365 wheat starch as raw material, starch samples were preheated in a RVA to simulate DSC heating profiles. The thermodynamic properties, long-range orderliness, short-range orderliness, and structure of wheat starch were determined by DSC, XRD, FTIR, LF-NMR and SEM to explore the phase transformation mechanism of Bainong 365 wheat starch at different water contents. The results show that at different moisture contents, when the endothermic transition temperature of starch samples determined by DSC was reached or exceeded, the enthalpy of starch was 0, all free water was converted into uneasy flowing water and bound water, and the surface structure of starch was severely damaged. At this time, starch was completely gelatinized, but the short-range and long-range ordered structures of starch determined by FTIR and XRD still existed and gradually decreased with increasing temperature. Therefore, it was concluded that the temperature range of the starch endothermic transition does not represent the temperature range of complete gelation of starch, and the structure destroyed by complete gelation of starch may not be simple short-range and long-range ordered molecular structures.