The invention relates to a method for degrading beta-1,4-glycosidic-bond-containing high-molecular-weight polysaccharides. The method comprises the following steps: introducing an 80-180 mg / mL beta-1,4-glycosidic-bond-containing high-molecular-weight polysaccharide solution into an electrolyzer provided with a cathode and an anode, regulating the solution to acidity, introducing 4.0-6.0L of oxygen to the cathode for every liter of the polysaccharide solution, and introducing a direct current while controlling the current density of the cathode at 10-13 mA / cm<2>; and under such conditions, carrying out degradation, and collecting the electrolyte. The method has favorable selectivity for beta-1,4-glycosidic-bond-containing polysaccharides, has the advantages of simple technical operation, time saving, high efficiency, mild reaction conditions and low environmental pollution, and is beneficial to scale-up production. More importantly, compared with the acid-process degradation and hydrogen peroxide degradation, the electro-Fenton process has higher degradation rate for polysaccharides, and the molecular weight range of the obtained low-molecular-weight polysaccharides is narrower.