Structure and morphology of single-crystalline hcp Co nanowires fabricated by electrodeposition were investigated in detail by various x_ray diffraction method s. The results confirm that the Co nanowires can be deposited in single crystall ine with the same crystal orientation of ［100］ along the longitudinal axes. The arrays were composed from those nanowires preferentially in ［100］ direction with very high parallelity, but the ［001］ axis of the nanowires randomly lies in the array plane. By slightly higher depositing voltage, some twisted deformat ion could happen in the nanowires with chiral behavior. A twisted model has been brought forward to explain the experimental results. Magnetization properties m easured by superconducting quantum interference device magnetometer at 300K indi cated that the twisted lattices in the wire significantly affected the anisotrop y of the nanowires due to the magnetoelastic effect, and consequently, the magne tic easy axis can be tuned to the longitudinal direction effectively.