The invention relates to a pyrotechnic gas generating agent composition and a preparation method thereof and belongs to the technical field of gas generating agent compositions. The pyrotechnic gas generating agent composition is composed of 3, 4-dinitrofurazanofuroxan, Fe2O3, CuO, oxidant, catalyst, cooling agent and binder. The preparation method includes: sufficiently mixing the oxidant, 3, 4-dinitrofurazanofuroxan, the catalyst and the cooling agent, and then sieving to obtain well-mixed powder; dissolving the binder in an organic solvent, adding into the powder for granulation, and drying to obtain solid particles; tabletting the obtained solid particles to obtain the pyrotechnic gas generating agent composition. The pyrotechnic gas generating agent composition is high in gas generating efficiency, generated gas is pure and free of environment pollution, content of water vapor generated by burning the generated gas is extremely low, using safety is improved, and the pyrotechnic gas generating agent composition has great application prospect.