A new metal-containing ionic liquid of [(C(4)H(9))(2)-bim](3)[La(NO(3))(6)] (bim = benzimidazole) was synthesized and the structure was characterized by X-ray crystallography, IR and elemental analysis. The molecule contained three independent cations of benzimidazolium and two independent anions of La(NO(3))(6)(3-). The center lanthanum had a cuboctahedral geometry by coordinating to twelve oxygen atoms from six nitrates. Moreover, the electrochemical properties of the title complex bulk-modified carbon paste electrode (La-CPE) have been studied, and the results indicate that the La-CPE has good electrocatalytic activities towards the reduction of hydrogen peroxide, nitrite, bromate and trichloroacetic acid (TCA). This modified electrode has good reproducibility, high stability, low detection limit, technical simplicity and the possibility of rapid preparation, which is important for practical application on electrochemical sensors.