To tailor coercivity and magnetic anisotropy, we have fabricated Co nanowire arrays in the pores of anodic aluminum oxide templates by electrodeposition. Microstructure measurements performed by X-ray diffraction show that Co nanowire arrays are hexagonal closepacked (HCP) structures with different crystalline textures. A wide range in change of coercivity from 925 to 3310 Oe at 300 K, with a maximum of up to 4050 Oe at 5 K, can be found for nanowire arrays with a diameter of 20 nm. This may be the highest value and the widest range of coercivity reported for Co nanowires prepared by electrodeposition method. This finding could be attributed to the adjustment of the microstructure of the cobalt nanowire arrays prepared in different experimental conditions. We have also investigated the relationship between the crystalline textures and the magnetic properties of Co nanowire arrays using micromagnetic simulation combined with microstructure measurements. The preferred orientation of nanowire arrays, such as (1000) or (0002), is a key factor in determining coercivity. This wide tailoring of coercivity makes possible more promising applications of Co nanowire arrays with fixed diameter and length.