In this study, the melt blending method was used to prepare the polystyrene/halloysite nanotubes (PS/HNTs) nanocomposites instead of in-situ bulk polymerization of styrene monomer in the presence of HNTs. Surface modification of HNTs with styrene-maleic anhydride copolymers (SMA) was performed in THF medium to improve the HNTs distribution and compatibility in the PS matrix. PS/HNTs nanocomposites were prepared in a twin-screw micro compounder containing 5, 10, and 15 wt.% of nanoclays. The influences of the surface modification of HNTs on the properties of the nanocomposites were studied by XRD, SEM, DSC, TGA, and tensile test. The SEM images showed that the modified HNTs samples were uniformly distributed in the PS matrix compared to the pristine HNTs. The thermal stability of nanocomposites was also improved by increasing of modified HNTs content. Consequently, the surface modification increased the dispersion of HNTs in the PS nanocomposites prepared by melt blending method.