Key words 12%-DKDP, wideband second-harmonic generation, Raman shift, damage threshold, deuterium content.K(D 0.12 H 0.88 ) 2 PO 4 crystals were chosen to be used for quadratic nonlinear medium of wideband frequency doubling at 1 μm. A key limitation on this application is that little information can be found in the previous reports. In this work, growth as well as structural and optical properties of this crystal were investigated in detail. Experimental results in comparison with KDP indicate that lattice parameter along a-axis changes much more than lattice parameter c and infra-red absorption edge shift by 0.08 μm accompanied with increasing of transmittance in the whole region. With the introduction of deuterium atom, peak of ν 1 (PO4) shifts to lower wave number and transverse stimulated Raman scattering was effectively suppressed. Extra-ordinary and ordinary indices were also measured as function of wavelength. Good crystalline perfection and great performance of damage threshold also indicate that 12%-DKDP is an appropriate choice in the application of wideband frequency doubling at 1 μm.