In order to explore the effects of ultrasonication and germination synergistic treatment on the structure and physicochemical properties of brown rice starch， spectroscopic analysis and electron microscopy were employed to compare the changes in α-amylase activity， starch morphology， crystalline structure， and physicochemical properties across four groups: untreated brown rice， ultrasonication and germination synergistic treatment brown rice， germinated brown rice， and ultrasound-assisted germinated brown rice. The results showed that ultrasonication and germination synergistic treatment increased the α-amylase activity and reducing sugar content in germinated brown rice by 0.9 times and 12.0 times， respectively； while decreased the starch content by 16.2% compared with brown rice. The synergistic role of ultrasonication and germination contributed to more pits and pores in the surface of brown rice starch granules， but still maintained the original morphological characteristics. The treatment did not significantly change the crystal form of brown rice starch， but remarkably decreased the relative crystallinity (P<0.05). Ultrasonication and germination synergistic treatment had a significant effect on the gelatinization viscosity of brown rice starch， where the gelatinization enthalpy value was increased by 0.6 times， and the breakdown viscosity was reduced by 22.4%. In conclusion， synergistic treatment of ultrasonication and germination significantly enhanced the α-amylase activity， and further affected the structural characteristics and physicochemical properties of brown rice starch. These findings suggest that ultrasonication and germination synergistic treatment enhances α-amylase activity in brown rice， subsequently altering starch structural characteristics and physicochemical properties， thereby providing a theoretical foundation for the improvement of brown rice starch products and the development of germinated whole grain foods.