This study examines the selective dispersion of nano-SiO2 in polystyrene (PS) and polyamide 6 (PA6) blends. With the coupling assistance of 3-methacryloylpropyl trimethoxysilane (MPS), nano-SiO2 surfaces are grafted with PS chains of different molecular weights (SiO2-MPS-PS) or reactive random copolymer of styrene (St) and 3-isopropenyl-,-dimethylbenzene isocyanate (TMI) to produce SiO2-MPS-P(St-co-TMI). The isocyanate groups of the reactive copolymer can react with the terminal group of the PA6 to form a graft copolymer, which helps in controlling the location of nano-SiO2 between the PS and PA6 phases. Field-emission scanning electron microscopy imaging combined with the rheological method was used to investigate the location and dispersion of nano-SiO2, as well as the morphology of the PS/PA6 blends, at low nano-SiO2 loading. Compared with pristine SiO2, the modified SiO2 with different chain lengths adjusted the PA6 phase with refined size and narrow size distribution because of the strong interaction with both phases. The SiO2-MPS-PS with appropriate length is the most effective. The use of nano-SiO2 along with the reactive compatibilizer provides synergistic effects for improving the compatibilization of PS/PA6 blends. POLYM. ENG. SCI., 57:1301-1310, 2017. (c) 2017 Society of Plastics Engineers