In order to achieve good dispersion of nano-SiO2 and increase the interactions between nano-SiO2 and PU matrix, nano-SiO2 was firstly modified with poly(propylene glycol) phosphate ester (PPG-P) which was a new polymeric surfactant synthesized through the esterification of poly(propylene glycol) (PPG) and polyphosphoric acid (PPA). Then a series of polyurethane (PU)/SiO2 nanocomposites were prepared via in situ polymerization. The surface modification of nano-SiO2, the microstructure and the properties of nanocomposites were investigated by FTIR, SEM, XRD and TGA. It was found that good dispersion of nano-SiO2 achieved in PU/SiO2 nanocomposite after the modification with PPG-P. The segmented structures of PU were not interfered by the presence of nano-SiO2 in these nanocomposites. (C) 2011 Elsevier B. V. All rights reserved.