The regular and uniform array of silver-nanowire array with different diameters and aspect ratio has been produced by using the anodic aluminium oxide (AAO) template method. The enhancement dependences on diameter and aspect ratio have been studied by using 4-mercaptopyridine (4-Mpy) as a probing molecule. An optimum diameter (95 nm) of silver particle for maximum enhancement factor has been obtained at 632.8 nm excitation. And the enhancement factor increased with the aspect ratio of the silver nanowire. These experimental results have been analyzed with the related electromagnetic models. (C) 2008 Elsevier B. V. All rights reserved.