Micronano structure films supporting local surface plasmons were prepared by vacuum thermal evaporation and annealing, and the chalcogenide glass Ge₂₈Sb₁₂Se₆₀ film was evaporated on this film. The dispersion characteristics of optical nonlinear enhancement were studied by the Z-scan technique under femtosecond laser pulse excitation. Nonlinear absorption enhancement was observed at 650 nm and 850 nm. The nonlinear refractive index changes from negative to positive with increasing wavelength. The principle of nonlinear absorption enhancement of chalcogenide glass Ge₂₈Sb₁₂Se₆₀ thin films was characterized and analysed by scanning electron microscopy and transmission spectroscopy. The nonlinear absorption gradually changed from single photon absorption to two-photon absorption with increasing wavelength. The resonance center frequency of chalcogenide glass films shifted due to the micro/nanostructures of silver films. The preparation of micro/nanostructures for enhancing the nonlinearity of chalcogenide glass is simple without a complex lithography process, which provides a new idea for the design of nonlinear photonic devices.