The invention discloses a molecular engram material for selectively removing TSNA in cigarette gas and a preparation and application method thereof. The preparation steps of the molecular engram material are as follows: activating and silanizing silica gel before synthesizing the molecular engram material; then dissolving a functional monomer into a pore-forming agent, adding a crosslinking agentand an initiator, and silanizing the silica gel and making the silica gel react in the vacuum; and in succession, removing template molecules from a high molecular material on the surface of the silica gel through a chemical or physical method. A plurality of cavities which are formed in the polymer are matched with the template molecules in space and have multi-action sites in the specificity arrangement. The cavities have high-efficiency selectivity for the TSNA molecules. When the molecular engram material is used for the selective harm reduction of cigarette gas, the material is preferably applied to a compound filter tip and the addition amount of the material can be freely adjusted. When the molecular engram material is added into the filter tip with the addition amount of 40 milligrams per cigarette, the material can reduce the content of the TSNA in the cigarette gas by 25.1 percent without affecting other components in the cigarette gas, thereby reaching the aim of selective harm reduction.