A new semi-organic nonlinear optical crystal Bisthiourea-zinc Acetate (BTZA) has been grown and characterized. The solubility study was carried out in aqueous solution. Crystals were grown from low temperature solution method by slow evaporation technique. Powder XRD and FTIR have confirmed the formation of the new crystal. UV-Vis-NIR spectra analysis showed good optical transmission in the entire visible region. The optical second harmonic generation conversion efficiency of BTZA was determined using Kurtz powder technique. The SHG efficiency was better than materials like KDP and CTA. (C) 2004 Elsevier B.V. All rights reserved.