Abstract:In order to develop the active efficacy in hawthorn，the influencing factors and optimal process parameters of extracting hawthorn water-soluble dietary fiber were studied.The optimum extraction conditions of water soluble dietary fiber from hawthorn were determined by single factor test and orthogonal test.The factors order was ultrasonic power，pH，ultrasonic time，amount of added enzyme.The test results showed that the optimal process was ultrasonic power 320 W，pH 4.4，ultrasonic time 11 min and enzyme dosage 0.5%.Under these conditions its yield reached 6.12%and its purity was 91.63%.Scanning by electron microscopy revealed that the water-soluble dietary fiber of hawthorn was grape-like；The particle size distribution was concentrated by particle size analysis，and the average particle diameter was 19.5 μm；X-ray diffraction analysis could be found that the crystallinity was 13.45%；Infrared analysis showed that the water-soluble dietary fiber of hawthorn had absorption peaks at 3 450 cm-1-2 900 cm-1，2 900 cm-1-2 800 cm-1and 1 647 cm-1and it was described as containing a hydroxyl group，a saccharide methylene group，a uronic acid group or the like.