Starch is an essential and widely distributed natural material, but its detailed conformation and thermal transition properties are not yet well understood. We present a rapid Mueller matrix imaging system to explore the structural characteristics of starch granules by using 16 measurements with different incoming and outgoing polarizations. Due to the minimum rotation of the optical elements and the self-calibration ability of this system, the full Mueller matrix images can be accurately obtained within ten-odd seconds. Both structural and molecular features of the starch granule were investigated in the static state and gelatinization process by means of multiple optical characteristics deduced from the Mueller matrix. The experimental results for the structural changes during the gelatinization were close to other nonlinear optical approaches; moreover, the crystallinity and optical rotation of the starch granule are also determined through the use of this approach.