The present work reports on a new silicotungstic acid catalyst supported on graphene (HSiW/G). The deposition was performed by sonochemical method proven as an effective technique for the synthesis of the supported catalysts. The catalyst (HSiW/G) was characterized using a variety of physico-chemical methods as TEM, HR SEM, DLS, FTIR and Raman spectroscopy. Homogeneous distribution of HSiW on the surface of graphene was demonstrated. Hydrolysis of biomass for the production of glucose was studied. The hydrolysis of glycogen was performed with a HSiW/G catalyst by hydrothermal treatment. The yield of glucose (65 wt%) obtained was about 8 times higher than that obtained with the same amount of bare HSiW. Stability of the HSiW/graphene even after 3 repeated uses was confirmed. The mechanism of enhancement of the catalytic activity was discussed in terms of a special interaction between the graphene support and HSiW and also the appearance of hydrophobic cavities on the surface of graphene.