Abstract: To reduce resource waste and enhance the utilization of dragon fruit peel, the study employed acid hydrolysis (A-SDF), enzymatic hydrolysis (E-SDF), and ultrasound-assisted extraction (U-SDF) to isolate soluble dietary fiber (SDF) from red-fleshed dragon fruit peel. The physicochemical, functional, and structural properties of the SDF extracted by these methods were analyzed and compared. The results showed that U-SDF demonstrated the highest water-holding capacity (32.06±0.66 g/g) and oil-holding capacity (5.36±1.54 g/g), while E-SDF exhibited the greatest swelling capacity (29.10±1.34 g/g). In terms of antioxidant activity, A-SDF showed the strongest scavenging ability against DPPH and hydroxyl radicals, whereas E-SDF exhibited the highest ferric-reducing antioxidant power (FRAP). All antioxidant activities displayed a clear dose-dependent pattern. Additionally, U-SDF exhibited the strongest cholesterol-binding capacity in a simulated intestinal environment (20.34 mg/g at pH7.0). Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed that all SDF types retained the cellulose Ⅰ crystalline structure. Scanning electron microscopy (SEM) revealed that U-SDF possessed a larger specific surface area along with finer flake-like structures, which contributed to enhanced adsorption capacity. The results demonstrated that ultrasound-assisted extraction offers a comparatively high SDF yield while significantly enhancing its functional properties, highlighting its potential as an effective approach for producing high-quality SDF from dragon fruit peel for use in food and nutraceutical applications.