Silver (Ag) films with different nanostructures were prepared by electron beam evaporation and characterized by spectroscopic ellipsometry in combination with X-ray diffraction and field emission scanning electron microscopy (FESEM). The percolation threshold and the nanostructures of Ag films can be deduced from the measured ellipsometric parameters (Ψ, Δ). According to the different topological properties of (Ψ, Δ) trajectories, the percolation threshold of Ag films was determined to lie between the coverage of 66 and 79.6%. The result was further confirmed by the plus−minus sign of the real part of the dielectric function in the infrared. Silver particles, coalescence, networks, and continuous nanostructures were clearly identified from the topological properties of the tangent azimuth of (Ψ, Δ) trajectories, which were verified by the FESEM results. This work is useful for monitoring the fabrication of nanostructure materials in the industry and research field. In addition, it has potential applications on the recognition of micro−nanostructures in the artificial intelligence field.