The optimum extraction process and bleach process conditions of alkali-insoluble dietary fiber from Enteromorpha prolifera was studied.Color was selected as the indicator of extraction,the optimum extracting was determined by orthogonal test.The functional properties of alkali-insoluble dietary fiber were preliminary determined.The results showed that the optimum extraction process conditions of alkali-insoluble dietary fiber was 1 g/L NaOH,alkaline cooking time 60min,HCl concentration1 g/L,the extraction rate could be as high as 21.97% with the color near light green.The optimum bleach process condition was: 0.7 g/L NaClO,solid-liquid ratio 1∶ 60,pH5,bleach time 45min.The production rates of dietary fiber could be as high as 16.88% with the color near to white.The dry base content,expansive capacity and water holding capacity of the alkali-insoluble dietary fiber from Enteromorpha prolifera were 70.49%.22.09mL/g and 510.58%,respectively.