L - Threonine hydrochloride (LTHCl) and zinc chloride doped L - Threonine hydrochloride crystals are aminoacid compounds which have been successfully grown by slow evaporation method . Single crystal X-ray diffraction studies reveal that the LTHCl and zinc chloride doped crystals belong to orthorhombic crystal system with space group P21 . UV-vis-NIR absorption spectrum shows that crystals have wide optical window in the range of 190-1100 nm. The functional groups of the grown crystals were analyzed by FT-IR spectral studies. The dielectric property of grown crystals was established by dielectric measurements. Vickers microhardness test was also carried out to elucidate the mechanical behavior of the grown crystals. FESEM - EDAX and ICP-OES studies confirm the presence of zinc chloride in LTHCl crystal . The second harmonic generation (SHG) behaviour of the grown crystals has been confirmed by Kurtz-Perry powder technique and the result shows that the incorporation of zinc chloride in LTHCl has improved the SHG efficiency.