The invention discloses a plasmon-structured substrate and a preparation method and an application thereof. The plasmon-structured substrate comprises a substrate, a reflective layer, an insulating layer, a metal nano-structure array and a positive electrode and a negative electrode; a perovskite device enhanced substrate is prepared based on a plasmon field enhancement principle initially; and byvirtue of a physical method, absorption limited expansion of the perovskite material in an infrared light waveband and absorption enhancement in the whole absorption region are realized, so that negative effects caused by chemical doping of a perovskite layer is avoided.