Three new bismuth phosphates, Li(2)ABi(PO4)(2)(A = K, Rb, and Cs), were synthesized through the high-temperature solution method. They all exhibit three-dimensional (3D) [Li2P2O8](4-)frameworks built by isolated PO(4)tetrahedra and Li-O chains but crystallize in two different space groups, which can be attributed to the effects of alkali metal cations that control the connection modes of units. Li2KBi(PO4)(2), Li2RbBi(PO4)(2)and Li2CsBi(PO4)(2)show SHG intensities about 5.0, 3.1 and 2.5 times that of KDP, respectively, and are all phase-matchable. To the best of our knowledge, Li2KBi(PO4)(2)exhibits the largest SHG response among the bismuth phosphates. The effects of cations on the SHG responses have been discussed in detail. Our results indicate that introduction of the Bi(3+)cation with large distortion and synclastic arrangement of the Bi-O polyhedra is crucial to produce the large SHG response for phosphate NLO materials.