The new nonlinear optical crystals BaAl2B2O7 and K2Al2B2O7 are readily grown by top-seeded flux method. BaAl2B2O7 crystallizes in the rhombohedral space group R32 (Z equals 3) in a cell of dimensions a equals b equals 5.001 angstrom, c equals 24.378 angstrom and V equals 528.01 angstrom3. K2Al2B2O7 crystallizes in the trigonal space group P321 (Z equals 3) in a cell of dimensions a equals b equals 8.530 angstrom, c equals 8.409 angstrom and V equals 529.9(2)angstrom3. The theoretical calculations and the measurement of nonlinear optical effect indicates that the two crystals are phase-matchable with the nonlinear optical coefficient d11 equals 0.75 pm/V for BaAl2B2O7 and d11 equals 0.48 pm/V for K2Al2B2O7. The birefringence of BaAl2B2O7 is (Delta) n equals 0.063 and 0.068 for K2Al2B2O7.