Abstract: Much watery insoluble dietary fiber in the sullage of Shiqian moss tea was extracted by the approach of alkali solution. Simultaneously, by applying theoretical approach of Design-Expert V8.0 software to extraction test, all of factors affecting extraction efficiency of watery insoluble dietary fiber, such as extraction temperature, ratio of stuff with solvent, base concentration and extraction time, were optimized completely with Box-Behnken (BBD) basis set. The results demonstrated that 32.6℃ as extraction time, 0.2mol/L as alkali concentration, 50 min as extraction time and 1∶13.5 (g/m L) in ratio of stuff with solvent, were best optimum extraction conditions.The extraction efficiency could arrive to 78.66%. In addition, in testing property of watery insoluble dietary fiber, water holding capacity was 183.92% and the swelling degree was 2.83 m L/g. Therefore, the response surface method in optimizing extraction of watery insoluble dietary fiber performed short time, low energy exhausted and high extraction efficiency in feature.