A new method for preparing SERS-active substrate was reported. The prefabricated silver substrate was immersed into the mixture of silver enhancer and initiator for several seconds and then rinsed by tridistilled water. The measurements of the UV-Vis adsorption spectra and AFM show that the average particle size increases with increasing the immersing time. The optimum immersing time is 20 s. Furthermore, the measurements of the SERS spectra of BPENB indicate that such substrate could be kept active for more than 90 d.