Unmodified and surface modified polystyrene (PS) nanoparticles with hydrophilic end group on surface were synthesized by emulsion polymerization for adsorption of a protein (immunoglobulin G, IgG) by passive adsorption and electrostatic attraction for the application on solid-phase immunoassay. The presence of formed IgG-PS particle complex was confirmed by dynamic light scattering (DLS) measurement which shows the increased size of particle (a parts per thousand 178nm and 220nm) after IgG immobilization. Increased Zeta (zeta) potential from -56.7mV to -3.84mV following the IgG immobilization by electrostatic attraction also provides the presence of the formed IgG-PS particle complex. Enzyme-linked immunosorbent assay (ELISA) results demonstrate that the formed IgG-PS complex was stable and the binding strength between IgG and PS was maintained after 1 month from initial IgG-PS particle complex formation.