MOCVD-grown single-crystal β-Ga2O3 epilayers on (0001) sapphire substrates were developed at low temperature and low pressure. As-grown β-Ga2O3 epilayers were post-annealed at different temperatures in the atmosphere. Crystalline structure and quality of epilayers, tracked by X-ray diffraction (XRD), remained almost unchanged after post-annealing. Effect of surface states and point defects of β-Ga 2O3 epilayers before and after annealing are studied using room temperature Photoluminescence (PL) and I-V characteristics (dark current). The significant difference in PL property and dark current before and after annealing is attributed to healing of the surface states and point defects, as β-Ga2O3 is known for its high density of oxygen vacancies. Post-annealing single-crystal β-Ga2O3 epilayers at high temperature makes the healing possible, probably due to oxygen diffusion and surface band bending. A significant healing of surface states and point defects in single-crystal β-Ga2O3 indicates its high potential in fabrication of optoelectronic devices.