Abstract: The ultrasonic microwave assisted enzymatic extraction of soluble dietary fiber(SDF)from seedless of Clausena lansium sarcocarp was optimized by response surface methodology.The physicochemical properties,monosaccharide composition and microstructure of SDF were studied. The results showed that the optimal preparation conditions of SDF were as follows:The ratio of material to liquid was 1:23 g/mL,ultrasonic time was 25 min,ultrasonic power was 280 W,and cellulase dosage was 0.64%. Under these conditions,the yield of SDF was 12.55%,the purity was 79.65 g/100 g,the net yield was 10.00%,the water holding capacity was 6.04 g/g,the oil holding capacity was 1.58 g/g,and the swellability was 39.25 mL/g. Infrared spectrum scanning showed that SDF of Clausena lansium sarcocarp had typical polysaccharide characteristics. Saccharonitrile-derived gas chromatography showed that SDF contained 4 kinds of monosaccharides,including arabinose,glucose,galactose,and mannose.The molar ratios were 12:7.5:3:1. Scanning electron microscopy showed that the SDF of Clausena lansium sarcocarp was compact and smooth folded. The research results could provide a reference for the development and utilization of SDF from Clausena lansium sarcocarp.