Gold nanoclusters (Au NCs) are a type of emerging ECL emitter with molecule-like properties and low toxicity that hold great potential for sensing application. However, the application of Au NCs in ECL sensing is still limited due to their low ECL efficiency. In this work, we provided an effective way to enhance the ECL efficiency of Au NCs. By doping Ag on GSH-protected Au NCs to form bimetallic clusters (GSH-Ag/Au NCs), the ECL efficiency of Au NCs was greatly improved. Based on the enhanced ECL signal of Au NCs, an ultrasensitive ECL sensor was constructed for the detection of dopamine (DA). DA exhibited a prominent ECL quenching effect towards the formed bimetallic GSH-Ag/Au NCs which can be used for DA detection. The proposed ECL sensor exhibited excellent sensitivity, selectivity and stability and had a wide linear range from 10 nM to 1 mM with a low detection limit of 2.3 nM (S/N = 3). More importantly, this work provided a potential method to improve the ECL properties of Au NCs and widen their analytical application.