The mechanism of aromatic C-H amination of benzene via a nitrene insertion approach catalyzed by the Tp(Br3)Cu(NCMe) complex was computationally investigated. The results of computational studies show that addition of the nitrene moiety of the Tp(Br3)Cu-nitrene intermediate to benzene, and therefore, to form an aziridine intermediate, is more favorable than the nitrene moiety induced hydrogen atom abstraction from a sp(2) C-H bond of benzene. Subsequently, the cleavage of a C-N bond of the aziridine intermediate followed by an H-atom transfer step might occur, due to the driving force of the rearomatization, to afford the desired aromatic C-H amination product. For toluene, computational results suggest that the benzylic C-H amination via hydrogen atom abstraction followed by radical rebound path is more favorable than the aromatic C-H amination via a nitrene addition path, which is in accord with experimental results.