An ultrathin film was formed by the electrostatic self-assembly of polyelectrolyte poly-N-ethyl-N,N-dimethyaminoethyl methacrylate (PDMAEB) and the organic dye metanil yellow (MY) on a smooth glass sheet. An atomic force microscope was used to study the topography and the phase of the two samples and the ultrathin film (PDMAEB-MY). The dynamic course of the surface structure was researched by atomic force microscopy also. It is illustrated that the existence of electrostatic interactions between PDMAEB and MY made MY arrange in order on the polyelectrolyte surface.