To improve the signal-to-noise ratio of an alcohol vapor detection system, the technical parameters of a dual-pass narrow-band filter are determined according to the Beer-Lambert's law. The narrow-band filter is designed via double-sided splitting on a Si substrate according to technical parameters to establish the refractive index gradient model, realizing accurate control of films. The vacuum chamber in-situ annealing method is used to increase the density and reduce the stress of the film layer, thereby improving its adhesion and stabilizing its spectral properties. Of the prepared film layers, over 90% can satisfy transmittance at wavelengths of (1392±10) nm and 1530-1570 nm; less than 1% can satisfy 400-1350-nm and 1600-1800-nm band transmittances; the transmittance is less than 30% in the 1410-1515-nm band.