With β-mannanase,Konjac glucomannan(KGM) was enzymatic hydrolyzed to its degraded products with moderate viscosity,which improved the defects of high viscosity of commercial KGM used in food industry.The standard KGM products were also achieved.The optimum conditions for hydrolysis was temperature 55°C,KGM mass fraction 12%(prepared by deionized water),enzyme concentration 3.0U/g,hydrolysis time 120min.Under these conditions,the viscosity of hydrolysates was controlled in the range of 1 800~2 000 mPa·s,molecular weight distribution was 91.01% in the range of 105~107.The KGM after hydrolysis is still polysaccharide macromolecules due to limited enzymatic hydrolysis.