Abstract: Sulphated konjac glucomannan (KGMS) was prepared by using sulfuric acid method. Controled the total volume of concentrated sulphuric acid and 1 -butanol that were 10mL. Then three reaction parameters including the volume ratio of concentrated sulphuric acid and 1 -butanol, reaction time and quantity of KGM were optimized by using central composite design and response surface methodology based on single factor investigations for achieving maximum degree of substitution (DS) of KGMS. The interaction of the respective variables and their influences on the DS of KGMS were studied by using Box -Benhnken central composite design and response surface analysis theory, and the simulated quadratic polynomial regression equation of prediction model was set up. Under the optimal condition of concentrated sulphuric acid and 1-butanol volume ratio of 3.22∶1, reaction time of 33min, KGM quantity of 0.59g, the average DS of KGMS was 0.93. FTIR analysis result showed KGMS formed two new absorption peak at 1257cm -1 and 814cm -1 , which were the characteristic peak of S=O and C-O-S groups, indicating the successful preparation of KGMS.