Abstract: The present invention relates to compounds and their nonlinear optical (NLO) crystals of A3B11P2O23 (A=K, Rb, Cs), their producing method and uses thereof. A3B11P2O23 (A=K, Rb, Cs) belong to triclinic crystal system, and have a space group of P1, crystal cell parameters of a=6.284(8)-8.784(3) ?, b=6.338(3)-8.838(3) ?, c=6.463(3)-8.963(3) ?, ?=70-105°, ?=75-106°, ?=76-107° and Z=1 and a unit cell volume of V=257.4(3)-696.0(6) ?3. A3B11P2O23 (A=K, Rb, Cs) compounds were prepared by a high-temperature solid-state reaction method or a hydrothermal method, and A3B11P2O23 (A=K, Rb, Cs) NLO crystals were prepared by a high-temperature solid-state reaction method, a hydrothermal method or a solution method. These materials can be used to manufacture second harmonic generator, up-down frequency converter, optical parametric oscillator, etc.