Abstract: Electron affinities (EAs) of most lanthanide elements still remain unknown due to their relatively low EA values. In the present work, the cryogenically controlled ion trap is used for accumulating atomic lutetium anion Lu^-, which makes the measurement of electron affinity of lutetium become practicable. The high-resolution photoelectron spectra of Lu^- are obtained via the slow-electron velocity-map imaging method. The electron affinity of Lu is determined to be 1926.2(50) cm^-1 or 0.23882(62) eV. In addition, two excited states of Lu^- are observed.