A new and efficient anodic Ru(bpy)32+ ECL system by using acridine orange (3,6-Bis(dimethylamino)acridine, AO) as a coreactant was reported in a neutral medium. The developed Ru(bpy)32+-AO system displayed a higher ECL intensity than that of the classic Ru(bpy)32+- oxalate ECL system, and was further exploited for the ECL detection of thiourea for the first time.