An aligned Ag nanowire array was directly synthesized by galvanic replacement on curved poly(ethylene terephthalate) (PET) by using a Cu2O microcrystal as a reductant. A more orderly aligned nanowire array was obtained when the curvature radius was reduced. A second growth with different orientation produced Ag nanowire networks. The guided growth was also achieved when using Zn as a reductant or polystyrene as a substrate. This plain method with facile control over the orientation and density of the Ag nanowire array enriches the grow-in-place methodology and can potentially be applied to various fields.