1,3-dimethyl-2-ferrocenylmethylbenzimidazole(a) is a novel benzimidazole complex.Based on the X-ray structure,the quantum chemical calculation was performed.This compound belongs to doublet system,and full geometry optimizations were carried out with ab initio restrict open-shell method ROHF.For this initialized structure,B3LYP and B3PW91 methods were used to re-optimize.Results of B3PW91 are better accordance with the experiments,so they were used to the later calculations,such as,energy,frontier molecular orbital components and net charges distribution etc.It is concluded that the complex is stable and the active sites are on Fe,C11 and C12 atoms.