Abstract: Ni nanowires are prepared by electrodepositing Ni into porous anodized aluminum oxide（AAO） template with nanosized pores.And then well ordered Ni nanowire arrays with controllable length are made from partial removal of AAO in mixture of phosphoric acid and chromic acid（6 wt% H₃PO₄: 1.8 wt% H₃CrO₄）.The images of Ni nanowire arrays are obtained by scanning electron microscope（SEM） and transmission electron microscope（TEM）,respectively.Selected area electron diffraction（SAED）are employed to study the crystalline morphology of Ni nanowire arrays.Also,the relations between the etching time and the mass reduction of AAO template,the length of Ni nanowire arrays are discussed.The results indicate that mixture of phosphoric acid and chromic acid is a more mild and effective etchant compared with NaOH aqueous solution.When using mixture of phosphoric acid and chromic acid as etchant,the length of nanowires exposed from template can be accurately controlled through controlling etching time.This etching method is generally applicable for many one-dimensional nanoarrays prepared from AAO template-assisted synthesis.