In this study, a sodium carbonate impregnated activated carbon (IAC) was applied as the adsorbent for low concentration hydrogen sulfide (H2S) in nitrogen under the anaerobic conditions in a fixed bed. The effects of impregnation, relative humidity, temperature, and the inlet H2S concentration on the adsorption process were intensively investigated. The data of adsorption capacity were correlated by Langmuir isotherm. The results showed that the data fitted the model well within the concentration range studied. The IAC demonstrated more than three times adsorption capacity for H2S under dry conditions, compared with the original activated carbon (AC). It was confirmed that increasing relative humidity enhanced H2S adsorption capacity on both AC and IAC, and the adsorption capacity of H2S decreased slightly with increasing temperature. To predict breakthrough curves, a one-dimension model for the fixed beds packed with porous adsorbents was proposed and numerically solved. Simulation results matched with the experimental data in most part of the breakthrough curves.