An elaborated aggregate of Co3O4 nanoparticles and Ru(bpy)32+ complexes (Co3O4@Ru) worked principled from synergism for enhanced coreactant electrochemiluminescence (ECL). Co3O4 acted as an oxygen evolution reaction (OER) accelerator and electrochemical catalyst, amplifying the ECL reaction between Ru(bpy)32+ and lidocaine, resulting in ultra-sensitive detection of lidocaine with a wide detecting range and nanomolar detection limit. A comprehensive ECL mechanism with synergism was proposed to complement the previously inconsistent studies of Co3O4 as functional amplified materials for Ru(bpy)32+-based coreactant ECL. The proposed sensor introduced NO2- as an amino scavenger, providing unprecedented selectivity in detecting lidocaine. Furthermore, the Co3O4@Ru aggregate modified electrode was successfully operated on human serum and commercial drugs, demonstrating its potential in medical monitoring. This research aims to improve the accuracy of detecting lidocaine and can pave the way for incorporating other exogenous nanomaterials into ECL sensors.