The adsorption characteristics of various small gas molecules (NO2, SO2, NO, NH3, H2S, H2O, O2, CO2, CO, N2, and H2) on GeSe were explored using first-principles calculations based on density functional theory. The findings indicate that the adsorption energy of NO2, SO2 and NO adsorbed on GeSe are largest, especially for NO2 which is up to 1.088 eV. After adsorption of NO, the system experiences the transition from non-magnetic to magnetic, which is different from NO2 and SO2 adsorption system. Besides, a thermodynamic statistical model was used to calculate the adsorption concentration of these systems. Moreover, NO2 exhibits a significantly higher adsorption density (7.307 × 1039 cm−2) compared to the other gas molecules. Additionally, the I-V curve has also been calculated by the nonequilibrium Green’s function method, and the significant rise in currents of NO2 adsorption system implies a marked change in electrical properties. These findings suggest that GeSe holds strong potential as a selective sensing material for NO2 detection.