Wheat bran was taken as raw material to extract bran starch by alkaline protease method and ultrasonic-assisted alkaline protease method respectively. After extraction conditions of the two methods were optimized, the granular structure and molecular structure of bran starch were analyzed. The results showed that the optimal extraction conditions by alkaline protease method were as follows: solid-liquid ratio 1∶10 (g∶mL), enzyme dosage 529.92 U/mL, enzyme reaction time 50 min, reaction temperature 45 ℃ and pH 12. The yield of starch was 30.40% and its content was 59.24%, while the powder was light brown; the optimal conditions by ultrasonic-assisted alkaline protease method were as follows: solid-liquid ratio 1∶15 g/mL, ultrasonic power 150 W and ultrasonic time 15 min. The yield of bran starch was 21.06% and its content was 90.64%, while the powder was white. The purity and extraction rate of bran starch extracted by ultrasonic-assisted alkaline protease method were better than those by single alkaline protease method. Analysis results showed that branch/straight ratio of the wheat bran starch was 4.69 and broken starch content was 1.78%. The starch bran particles were ellipsoidal, with an average particle size of 15.86 μm and radial crystal structure of A-type.