Removal of boron from silicon is a tough task by traditional directional solidification and vacuum refining techniques, due to its large and inappropriate segregation coefficient and low saturated vapor pressure. At high temperature boron react with oxygen to form volatile boron oxides which can be evaporated. So, the removal procedure of boron from silicon melt is investigated by incorporating a small amount of water vapor above the melted surface. The results show that boron is oxidized to mainly form BO and evaporated with 28% removal efficiency by average. It is considered that oxygen atoms experience a series of physical and chemical processes, such as a chemical reaction in the bulk of the melt, evaporation from the melt surface, transportation across the gas phase and ionization due the electron beam, which is conducive to the continuous removal of boron.