Two new tartratoborate nonlinear optical materials, KSr[C4H2O6B(OH)(2)]center dot 4H(2)O (KSCB) and RbSr-[C4H2O6B(OH)(2)]center dot 4H(2)O (RSCB), have been prepared through slow evaporation at room temperature. Single-crystal X-ray diffraction data reveal that KSCB crystallizes in the triclinic system, space group P1 (no. 1). It consists of KO8 polyhedra, SrO9 polyhedra, BO4 tetrahedra, tartrate molecules and H2O molecules. The isolated tartratoborate anions are connected to form a three-dimensional network structure by sharing oxygen atoms with K+ and Sr2+. The structural data show that KSCB and RSCB are isostructural and noncentrosymmetric. KSCB and RSCB produce second-harmonic generation intensities of 1.5 x KH2PO4 and 1.7 x KH2PO4, respectively, and they are both type I phase-matchable. The UV-Vis diffuse reflectance spectra of these compounds indicate that they are both transparent from 250 to 850 nm. Related infrared spectra and thermal analyses were also performed.