In this paper, the formulas of diffusion coefficient (D) and mass transfer coefficient (beta) of boron in molten silicon were deduced. The diffusion coefficient of boron was determined to be 1.46 x 10(-8) m(2) s(-1) by the diffusion experiment at 1823 K in the resistance furnace. The mass transfer process of boron between silicon and slag was described using the two-film theory and the mass transfer coefficient (beta) of boron was measured to be 1.7 x 10(-4) m s(-1) while using the binary CaO-SiO2 slag refining at 1823 K. It was calculated by the relation between diffusion coefficient and mass transfer coefficient that the effective boundary layer thickness (delta) close to molten silicon side was 0.086 mm. (C) 2015 Elsevier B.V. All rights reserved.