The polymer layers adsorbed oil silica particles in rubber-silica systems have been investigated with the contrast variation small-angle neutron scattering (SANS) method. The scattering intensities of specimens swollen by solvents with various scattering length densities were measured. The contrast variation SANS for the specimens yielded partial scattering functions: the scattering function for polymer-polymer correlation S-PP(q). the scattering, function for silica-silica correlation S-SS(q), and the scattering function for polymer-silica correlation S-PS(q). The analyses of S-SS(q) explored the hierarchical structures formed by silica particles. The analyses of S-PS(q) and S-SS(q) clarified the existence of dense polymer layers around silica aggregates. Several characteristic parameters are estimated from the analyses, Such as the size of aggregates, the thickness of layers, the volume fractions of polymer of layers and matrix, and the correlation length of the matrix network. The contrast variation SANS is found to be a powerful tool for the analyses of the Structures of the rubber-filler systems.