High optical quality ultraviolet nonlinear optical (NLO) crystal K3B6O10Br (KBB) with dimensions of 42 mm×20 mm×18 mm was successfully grown by the top-seeded solution growth method. According to its structural symmetry requirements, the crystal was cut and fabricated into different devices for the complete characterizations of its photoelectric properties. Additionally, the electric-elastic constants of the KBB crystal were systematically characterized, and the significant differences in piezoelectric anisotropy are observed due to its microscopic structure. The maximum piezoelectric constant d33 is measured to be 6.69 pC/N. Considering its good NLO frequency conversion, electro-optical and piezoelectrical properties, KBB crystal shows potential applications in the optoelectronics fields.