Highly active and economic catalysts for oxygen reduction reaction (ORR) are always important for renewable energy technique. Since more than half of the voltage loss in fuel cell comes from the cathodic ORR process, and most of the commercial available catalysts for ORR is Pt-based. Herein, a new Ag-Cu bimetallic nanostructure was developed by electrochemical method, the fabricated Pt-free material shows a great performance towards ORR, which is comparable to the Pt/C commercial catalyst. The selectivity of the catalyst was carefully studied by scanning electrochemical microscope (SECM). Result shows the ORR by Ag-Cu bimetallic nanostructure prefer a four-electron reduction process, with H2O as the main product and trace amount of H2O2 can be detected. However, similar pure Ag nanostructure presents a much lower selectivity, which indicates the introduction of Cu is essential. Possible model was established to explain the enhancement as well. This Ag-Cu bimetallic nanostructure suggests a potential to be developed as cathodes in fuel cell, with a highly activity and relative low cost.