The digestion rate of starch directly affects postprandial blood glucose levels, and regulating starch digestibility is important for the development of health-oriented starch-based foods. In this study, high amylose maize starch was used to prepare preformed V-type starch. Gallic acid (GA) was introduced to form starch complexes, and ultrasound treatment was applied during the complexation process. The effects of GA complexation and ultrasound treatment on structure and in vitro digestibility of starch complexes were systematically investigated. X-ray diffraction analysis showed that pre-treatment resulted in the formation of V-starch, and GA complexation and ultrasound treatment did not alter the crystalline pattern. The GA loading content in starch complexes was 13.52 mg·g-1 DW and increased to 15.39 mg·g-1 DW after ultrasound treatment. Fourier transform infrared spectroscopy showed that no new characteristic absorption peaks appeared in all treated samples. Short-range order analysis showed that GA complexation increased the structural order of starch complexes, whereas ultrasound treatment reduced the degree of order, although the value remained higher than that of preformed V-starch. Particle size distribution and morphological analysis showed that GA complexation promoted particle aggregation, whereas ultrasound treatment improved system dispersion. In vitro digestion results showed that the complex obtained by ultrasound-assisted complexation exhibited the lowest digestion rate (0.033 min?1) compared with preformed V-starch. The results demonstrate that the combination of GA complexation and ultrasound treatment effectively reduces starch digestibility. The findings provide new insights into starch functionality regulation and the design of starch-based food systems.