The influences of refining agent Na2SO4+C and CeO2+NaNO3 on visible light transmittance of ultra-white flat glass are investigated. Results show that the visible light transmittance of glass enhanced from 91.30% to 91.87% with the increment of pyrolysis refining agent Na2SO4+C. But for the oxidoreduction refining agent CeO2+NaNO3, visible transmittance of glass remained unchanged when the mass fraction of CeO2 was less than 0.07% and increased obviously when the amount of CeO2 exceed 0.07%. Although the visible transmittance of ultra-white glass decreased due to the coloring ion Ce4+ and ultraviolet cut-off effect, no more than 0.07% is recommended. In face, the higher oxidizability of CeO2+NaNO3 rather than Na2SO4+C is helpful for reducing the value of Fe2+/FeTotal.