In this paper, the adsorption properties of CuO-HfSe₂ and ZnO-HfSe₂ substrates towards SF₆ decomposition gas (H₂S, SO₂, SOF₂ and SO₂F₂) were analyzed based on the first-principle calculations. The optimal position of the two metal oxides doping on HfSe₂ was calculated, and the binding energies of –2.530 eV and –1.906 eV ensure the stability of CuO-HfSe₂ and ZnO-HfSe₂ during adsorption process. The results show that, the modification of CuO and ZnO changes the band structure of the HfSe₂ monolayer, and the CuO and ZnO molecules are charged with –0.0339 e and –0.0368 e, showing the potential of adsorbed gas. Compared to the pristine HfSe₂ monolayer, the adsorption distances of CuO-HfSe₂ and ZnO-HfSe₂ to the four gases decrease from about 3.5 Å to about 2 Å, and the adsorption energies increase from about –0.35 eV to more than –2.1 eV and more than –1.1 eV, respectively. Moreover, charge deformation density, density of states, partial density of states and molecular orbital theory were explored to clarify the interaction between the gas molecules and the substrates. The results show that, CuO-HfSe₂ shows better adsorption performance than ZnO-HfSe₂ for H₂S, SO₂, SOF₂ and SO₂F₂. For CuO-HfSe₂ system, the adsorption capacity for the four gases is ranked as: H₂S > SO₂ > SOF₂ > SO₂F₂; and the sort is: SO₂ > SOF₂ > H₂S > SO₂F₂ for ZnO-HfSe₂ system. After gas adsorption, the conductivity of the system changes to different degrees, through which the adsorption of the gas can be detected. All adsorption systems have a long recovery time, and the methods of increasing the temperature or UV irradiation are needed to excite the gas desorption process. This study provides new sensing materials for H₂S, SO₂, SOF₂ and SO₂F₂.