Abstract: Ni-doped ZnO crystals were synthesized by the hydrothermal method.XRD indicated that,the solid solution Ni²⁺/Zn²⁺O was synthesized when Ni doping content was 1%,2%,NiO appeared when the Ni doping concentrations was up to 5mol%.FT-IR spectra showed that when the hydrothermal temperatures reached 160℃,there were more open voids in the lattice,and more Ni²⁺ replaced Zn²⁺ in solid solution,a new absorption band appeared near 910cm^-1,and the absorption band became stronger and wider with the increase of doping content;With enhanced of pH value,the more Ni²⁺ was actually getting into the ZnO lattice,the more defects occurred in the lattice,then a blue shift of absorption band was observed.And sample had a better infrared absorption in both mid and far-infrared.