The main focus of this work is the experimental observation of the static structure of the grafted chain conformation in a good solvent or in a melt. Therefore, the structural properties of the grafted chains in given conditions were investigated by small angle neutron scattering (SANS), small angle x-ray scattering (SAXS), and dynamic light scattering (DLS) to get insight into the conformation feature of the grafted chains on the spherical substrate, which is expected to be clearly discernible from that of the bulk chains in the same conditions. Polystyrene (PS) was grafted from the surface of silica nanoparticles (diameter 50 nm) and deuterated polystyrene (d-PS) nanoparticles (diameter 40 and 60 nm) using different synthesis methods. The particles had variation in grafting densities and molecular weights of grafted PS, which was expected to influence the conformation of the grafted chains either in a good solvent or in a polymeric matrix. First, the grafted particles were dispersed in good solvents for the experiments, and the results demonstrated that the grafted PS layer on the silica and d-PS particle with a small core size retained the slightly stretched conformation compared to that in the bulk state. For the d-PS particles with a large core, moreover, the grafted chains retained more highly stretched conformation compared to the silica and small d-PS. Second, the conformation of the grafted chains in a melt was investigated by SANS and SAXS. Variation in the molecular weights of the matrix polymer of d-PS allowed for the direct observation of change in the conformation of the grafted PS by means of SANS. The conformation change of the grafted PS was observed for the silica and d-PS particles with a large core and was related to the chain autophobicity driven by wetting or dewetting of the matrix chains. The critical value of the ratio of the molecular weight of the matrix to the grafted PS, where the wetting-dewetting occurs, was found to be small for the d-PS of a large core and large for the silica, which may originate from the difference in grafting densities of the two particle systems.