The invention discloses a poly3,4-diethyl hydroxy thiophene gas sensitive material and a preparation method thereof and belongs to the technical field of organic electronic materials. In the invention, a thiophene monomer is introduced to ethyl hydroxyl as an organic phosphorus sensitive functional group by a sample format reaction; and a thiophene organic phosphorus sensitive polymer material of which one branched chain contains the ethyl and hydroxyl is obtained by an oxidative polymerization reaction. Since the hydroxyl is introduced to the thiophene, the polymer sensitive material disclosed by the invention can be used for selectively adsorbing nerve gas and a stimulant thereof so as to enhance the sensitivity and the selectivity of the sensitive material. Meanwhile, according to the poly3,4-ddiethyl hydroxy thiophene gas sensitive material provided by the invention, the ethyl and hydroxyl are introduced to a thiophene repetitive unit, so that the sensitivity is further enhanced. The poly3,4-diethyl hydroxy thiophene gas sensitive material disclosed by the invention can be used for detecting the nerve gas.