This research study discussed the hydrogen sulfide (H2S) behavior during the absorption on ethylenediamine(2HNCH2CH2NH2) in the course of the sour gas sweetening process. For this purpose, the molecular dynamics simulation was conducted on methane, ethane, and hydrogen sulfide (as sour gas) and ethylenediamine for investigating the oil sweetening process. Quantum method of density-functional theory with B3LYP method and basis set 6-311(+)G** was also employed to calculate the charge. Simulation results revealed that, the ethylenediamine molecules could absorb the hydrogen sulfide molecule. Despite the six sites on the ethylenediamine, hydrogen sulfide molecules will interact just with two sites. It was also observed that each ethylenediamine molecule could absorb 3-7 hydrogen sulfide molecules, whereas hydrogen sulfide interacted only with two nitrogen sites. In addition to interaction with ethylenediamine, hydrogen sulfide molecules also interact with each other. This gives rise to the condition in which the number of hydrogen sulfide molecules acting with ethylenediamine would be more than two molecules. Investigating the behavior of the H2S molecules absorbed on nitrogen showed the unique interacting behavior of these molecules and nitrogen of ethylenediamine. H2S molecules are absorbed by nitrogen through one of its hydrogen molecules. However, it was observed that the two hydrogen atoms exchange their places with each other, and nitrogen will interact by another H atom of H2S. At some steps of simulation, the hydrogen absorbed on one of the nitrogen atoms of ethylenediamine, will immigrate to the other nitrogen atom of ethylenediamine molecule and interact with that nitrogen.