The reaction mechanisms of HNCS with NH(X3Σ) were theoretically investigated. The minimum energy paths(MEP) of the reaction were calculated by using the density functional theory(DFT) at the B3LYP/6-311[KG-*3]+[KG-*3]+G ** level. The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zero-point energies(ZPE) of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD(T)/6-311[KG-*3]++G ** level. It was found that the mechanisms of the HNCS+NH(X3Σ) reaction involve two channels producing the HNC+HNS and the N_2H_2 + CS products. Channel 1 plays a dominant role and the HNC+HNS are the main products. The reaction is exothermic. The minimum energy paths (MEP) of the reaction were calculated by using the density functional theory (DFT) at the B3LYP / 6-311 [KG- * 3] + [ The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zero-point energies (ZPE) of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD (T) / 6-311 [KG- * 3] ++ G ** level. It was found that the mechanisms of the HNCS + NH (X3Σ) reaction involve two channels producing the HNC + HNS and the Channel 2 plays a dominant role and the HNC + HNS are the main products. The reaction is exothermic.