Electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) has been widely used in analytical chemistry. Herein, we present a new approach to enhance the ECL of Ru(bpy)(3)(2+) by the localized surface plasmon resonance (LSPR) of gold nanorods (AuNR). Our investigations reveal that the ECL intensity could be greatly enhanced by controlling the distance between Ru(bpy)(3)(2+) and the surface of AuNRs. We call this kind of surface plasmon induced ECL enhancement as surface-enhanced electrochemiluminescence (SEECL). This kind of SEECL phenomenon is utilized to fabricate a biosensor for ultrasensitive Hg2+ detection. The SEECL biosensor is fabricated by self-assembling AuNRs and T-rich ssDNA probes on gold electrode surface. With the presence of Hg2+, the conformation of ssDNA probes changed to be hairpin-like structure via formation of T-Hg2+-T structure. And Ru(bpy)(3)(2+) could insert into the grooves of the hairpin structured DNA probes to generate ECL emission, which could be enhanced by the LSPR of AuNR. The ECL intensity of the sensor increased with the concentration of Hg2+, and a detection limit of 10 fM Hg2+ in aqueous solution was achieved. The effect of different LSPR peak location of AuNR on the sensitivity of biosensor has been investigated. The results show that a good overlap between the LSPR absorption spectrum and the ECL emission spectrum of Ru(bpy)(3)(2+) could achieve the best ECL signal enhancement. (C) 2014 Elsevier Ltd. All rights reserved.