A sizable single crystal with sizes up to 20 mm × 20 mm × 9 mm of K3B6O10Br with high transparency has been grown by top seeded solution method using KF and PbO as the fluxes at the cooling rates of 0.2-0.8 °C/day, in the temperature range of 570-610 °C. Crystal morphologies and growth habits of K3B6O 10Br grown using [101] and [211] direction seeds were studied. The volatility of the crystal growth systems was investigated by TG-DSC, which shows that the volatilization status is sensitive to the crystal growth temperature. The grown crystals were characterized by powder X-ray diffraction, infrared spectroscopy and transmittance spectrum.