Cu n BO 2 (OH) − (n=1, 2) clusters were studied by anion photoelectron spectroscopy and density functional calculations. From the experimental photoelectron spectra, the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of CuBO 2 (OH) − are determined to be 4.00±0.08 and 4.26±0.08eV, and those of Cu 2 BO 2 (OH) − to be 2.30±0.08 and 2.58±0.08eV. The structures of Cu n BO 2 (OH) − and their corresponding neutrals are assigned by comparison between theoretical calculations and experimental measurements. Both experiment and theory show that CuBO 2 (OH) can be viewed as a superhalogen, thus, confirmed that OH can behave like a halogen atom to participate in superhalogen formation.