To study the effect of different surface structures on the aggregation level and interfacial adhesion, nano-Sb2O3 particles were treated with cetyltrimethylammonium bromide (CTAB), silane coupling agent KH550 and their compounds (CTAB + KH550). The surface properties and morphologies of the nano-Sb2O3 particles were characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The aggregation level and interfacial adhesion of nano-Sb2O3 particles within PBT matrix were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), and quantitatively evaluated by some semi-empirical parameters including aggregates size (Dagg ), real filling degree (Vre ), interfacial adhesion ( B ) and aggregated interfacial adhesion (Bagg ) from the tensile strength and the Young’s modulus measurements. The results showed that the highest interfacial adhesion and lowest aggregation level were obtained for the CTAB + KH550 modified nano-Sb2O3/PBT composites followed by the KH550 modified, CTAB modified and bare nano-Sb2O3/PBT composites, respectively.