The local morphology and its evolution of an air-liquid-solid three-phase contact line was studied on the homogeneous surfaces of homopolymer of polystyrene (PS) and poly(methyl methacrylate) (PMMA) and the nanostructured Surface of diblock copolymer of PS-b-PMMA by the approach of the morphological study of the residual solid after droplet evaporation of water-soluble polymers such as poly(vinylpyrrolidone) (PVP) and poly(acrylic acid). The observation by atomic force microscopy discovered the stripelike "button-and-ribbon" structure of the precipitated polymer solute along the moving direction of the contact line. On the surface of PS-b-PMMA, the morphology of PVP has a close correlation with the nanostructure of PS-b-PMMA. The results exhibit the local morphology of the contact line and its evolution, revealing its pinning and depinning processes on the nanometer scale.