This study investigates the effects of ultrasonic, microwave, and ultrasonic-microwave synergistic modifications on the physicochemical properties, microstructure, and functional properties of corn bran insoluble dietary fiber (CBIDF). The results show that CBIDF exhibits a porous structure with loose folds, and the particle size and relative crystallinity are slightly decreased after modification. The ultrasonic-microwave synergistic treatment significantly enhances the adsorption capacity and cholate adsorption capacity of CBIDF. Additionally, it improves the in vitro hypoglycemic activity by enhancing glucose absorption, retarding starch hydrolysis, and facilitating glucose solution diffusion. The study also finds that the level of soluble dietary fiber is positively correlated with CBIDF adsorbability, while the crystallinity of CBIDF is negatively correlated with α-glucosidase and α-amylase inhibition activity, as well as water-holding and oil-holding capacity. The ultrasonic-microwave synergistic modification technique is proposed as an eco-friendly approach to enhance the value of corn bran resources by producing CBIDF products with improved functional properties.This study investigates the effects of ultrasonic, microwave, and ultrasonic-microwave synergistic modifications on the physicochemical properties, microstructure, and functional properties of corn bran insoluble dietary fiber (CBIDF). The results show that CBIDF exhibits a porous structure with loose folds, and the particle size and relative crystallinity are slightly decreased after modification. The ultrasonic-microwave synergistic treatment significantly enhances the adsorption capacity and cholate adsorption capacity of CBIDF. Additionally, it improves the in vitro hypoglycemic activity by enhancing glucose absorption, retarding starch hydrolysis, and facilitating glucose solution diffusion. The study also finds that the level of soluble dietary fiber is positively correlated with CBIDF adsorbability, while the crystallinity of CBIDF is negatively correlated with α-glucosidase and α-amylase inhibition activity, as well as water-holding and oil-holding capacity. The ultrasonic-microwave synergistic modification technique is proposed as an eco-friendly approach to enhance the value of corn bran resources by producing CBIDF products with improved functional properties.