The change of starch granule during gelatinization was determined by Focus Beam Reflectance Measurement(FBRM),which was an online monitor of the change of starch granule.Besides,a method to determine gelatinization degree by the total number of starch granules was proposed.The method simplifies previous method and provides useful reference model for the research of pasting property of starch.The results showed that: the number of corn starch measured by FBRM was first increased and then decreased,and the number decreased sharply at 70℃;the number of potato starch measured by FBRM showed a steadily decreased,and also had sharpest decline at 70℃;the number of tapioca starch measured by FBRM showed steadily decreasing with the sharpest decline at 65℃.The highest gelatinization degree for corn starch was 60.05% at70℃ and,potato starch was 38.83% at 70℃ and tapioca starch was 54.66% at 65℃;When the temperature reached 75℃,the total gelatinization degree of corn starch,potato starch and tapioca starch came to 93.55%,90.19% and 85.85%,respectively.None of them reached to 100%.