¹Department of Chemistry, Payame Noor University, 19395-4697, Tehran, Iran DOI : 10.35333/jrp.2019.25 In this paper, biosensors of the Fe-Nitrogen-doped zigzag (8, 0) carbon nanotube and Fe-doped zigzag (8, 0) carbon nanotube were offered for detection of dopamine molecule. The adsorption property and sensing mechanism of Fe-doped zigzag (8, 0) carbon nanotube and Fe-N-SWCNT (8, 0) with dopamine were investigated based on density functional theory. The obtained results demonstrated that both Fe-SWCNT and the Fe-N-SWCNT had good adsorption for dopamine, also conductivity also grew when they interacted with it. When dopamine is adsorbed on the surface of the single wall carbon nanotube, a large number of electrons transfer from the Fe-N-doped zigzag (8, 0) single carbon nanotube to dopamine, resulting in lessened frontier orbital energy gap and increased electrical conductivity. On the other hand, when dopamine is adsorbed on the surface of the SWCNT, the electrons transfer from dopamine to the Fe-N-SWCNT, the frontier orbital energy gap rises, while the electrical conductivity declines. Thus, Fe-nitrogen- SWCNT (8, 0) is more suitable and sufficient than Fe-SWCNT (8, 0) for dopamine detection. Keywords : Doped-single wall carbon nanotube (SWCNT); dopamine; density functional theory (DFT); interaction