Reflection−absorption infrared (RAIR) and surface-enhanced Raman scattering (SERS) spectroscopy were used to determine the orientation of the bulk and interface of a polymer thin film formed by atactic poly(methyl methacrylate) (a-PMMA) which was dip-coated onto a novel dual-sided substrate. The novel substrate with silver particles deposited on both sides of a glass slide by silver mirror reaction had two sides with different roughness and reflectivity. The top side (rough) and the bottom side (smooth) were suited for the SERS and RAIR analyses, respectively. The experimental results suggested that the molecular chain axis of bulk a-PMMA tended to parallel orientation to the silver substrate a little. However, the polymers at interface obviously oriented parallel to the substrate. A conformation transition of ester groups of a-PMMA after annealing at high temperature was confirmed using SERS and RAIR techniques.