Optical electron polarimetry is suitable for calibration of a spin-polarized electron source, especially for measurement of polarization of spin-polarized electron beam. In this paper, a new optical electron polarimeter is described,which is based on the circularly polarized He radiation induced by the bombarding of He atoms with spin-polarized electrons. The theoretical basis of the optical electron polarimetry and the structure of the optical electron polarimeter are discussed. The measurement of polarization of spin-polarized electrons produced from a new GaAs (100) spin-polarized electron source is carried out. The result of polarization of 30.8% for our spin-polarized electron source is obtained using the He optical electron polarimeter.