Abstract: The present invention relates to the field of nonlinear optical crystal materials and provided herein a Li4Sr(BO3)2 compound, a Li4Sr(BO3)2 nonlinear optical crystal as well as preparation method and use thereof. The Li4Sr(BO3)2 nonlinear optical crystal has a second harmonic conversion efficiency at 1064 nm of about two times that of a KH2PO4 (KDP) crystal, and an UV absorption cut-off edge less than 190 nm. Furthermore, the crystal did not disintegrate. By flux method with Li2O, Li2O—B2O and Li2O—B2O3—LiF used as flux agent, large-size and transparent Li4Sr(BO3)2 nonlinear optical crystal can grow. The Li4Sr(BO3)2 crystal had stable physicochemical properties, moderate hardness, and was easy to cut, processing, preserve and use. Therefore it can be used for preparing nonlinear optical devices and thus for developing nonlinear optical applications in the ultraviolet and deep-ultraviolet band.