The near-spherical silica nanoparticles with polyvinyl alcohol (denoted as PVA-SiO2) or polyethylene glycol (denoted as PEG-SiO2) as surface modifiers were loaded onto graphene oxide nanosheets (denoted as GO) to prepare PVA(PEG)-SiO2-GO nanocomposites. The nanocomposites well dispersed in water were then compounded with maleic anhydride (MA) - acrylic acid (AA) copolymer (denoted as PMAAA) to prepare new nanocomposite tanning agents (denoted as PVA(PEG)-SiO2-GO/PMAAA). The hydrothermal stability, thickness increase, mechanical properties, flame retardancy and antistatic property, etc. of the leather tanned with PVA(PEG)-SiO2-GO/PMAAA were founded to be improved in a significant way compared with those of the leather tanned with the commercial acrylic resin (CHINATAN OM) and pure PMAAA copolymer tanning agents. The acquired excellent tanning properties may be related to the synergistic tanning effects of near-spherical silica nanoparticles and thin-layered graphene oxide nanosheets in leather tanning process. Especially, the highest shrinkage temperature of the wet-white sheepskin tanned with PVA-SiO2-GO/PMAAA reached 71 degrees C and the thickness increase reached 190% without chrome tanning agents. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.