The invention relates to a vapor phase inhibitor and a preparation method thereof, and belongs to the technical field of oil field chemicals. The vapor phase inhibitor is composed of following components in percentage by weight: 55 to 70% of nitrogen containing cyclic organic compound, 5 to 10% of synergist, and 20 to 40% of coupling agent. The nitrogen containing cyclic organic compound is prepared by compounding aromatic heterocyclic compounds with amino alicyclic compounds according to a mass ratio of 1:1-3. The nitrogen containing cyclic organic compound comprises polar corrosion-inhibiting groups such as mercapto- (-SH), amino- (-NH2), and the like, and can form a stable complex after the nitrogen containing cyclic organic compound is adsorbed on the iron surface. Adsorption layers are formed in molecules or between molecules through hydrogen bonds, at the same time, the cyclic compound has a special rigid structure, thus hydrogen sulfide can be baffled effectively, the contact between H<+> and a metal surface is prevented, and the corrosion of sulfur and sulfides on the devices and pipelines in a gas field with a high sulfur content is prevented.