The invention discloses a sensitive element etching type non-refrigeration infrared narrowband detector and a preparation method thereof. The detector is composed of an aluminum oxide substrate, a metal reflecting layer, a manganese cobalt nickel oxide sensitive element, a manganese cobalt nickel oxygen medium super surface structure layer, a germanium single crystal hemispherical lens and a device tube socket. By precisely controlling the structural parameters of the etching sensitive element, the manganese cobalt nickel oxygen medium super surface structure layer of a specific pattern is formed, and an effect of perfect absorption of light of a specific wavelength by the device can be achieved; and meanwhile, the light of a non-specific wavelength is reflected to improve the narrowband detection capability of the device. In the structure of the sensitive element etching type non-refrigeration infrared narrowband detector disclosed by the invention, since no metal artificial microstructure of a plasmon type is introduced, a large amount of energy loss in the metal structure is avoided, thereby ensuring that the absorption of the sensitive element in the device reaches 80% or more,and the quality factor (Q value) of a spectral curve can reach about 15, which has very important significance for improving the response ratio and target recognition accuracy of the non-refrigeration infrared narrowband detector.