Large transparent KBBF crystal up to 70x60x2.5 mm(3) has been successfully grown with a modified KF-B2O3 flux system. The optimal viscosity of the high temperature solution was determined and the effect of B2O3 was discussed. The volatile contents from the growth solution were mainly composed of BeO, BF3 and KF as determined by TG-MS. Photoluminescence at room temperature was studied for KBBF family crystals at an excited wavelength of 230 nm. The emission peak at 369 nm was ascribed to Zn impurity.