Using sodium alginate as reducing agent and stabilizer, Ag-Au bimetallic nanoparticles (Ag-Au NPs) were synthesized by a simple and green method. The prepared nanoparticles were characterized by UV-Vis spectra, transmission electron microscopy, X-ray diffraction and differential light scattering. The results demonstrated that the synthesized nanoparticles had good dispersibility, mainly spherical with an average particle size of 20nm. Through the modified electrode, the application of Ag-Au NPs in the electrochemical catalysis of hydrogen peroxide had been tested and analyzed. The results showed that the modified electrode with Ag-Au NPs had good catalytic activity, high sensitivity and selectivity to H2O2 detection. The estimated sensitivity for H2O2 sensor was 260.08 mu Acm(-2)mM(-1), and the detection limit was calculated to be 0.18 mu M estimated (S/N=3). Additionally, a linear relationship was obtained from 30 to 300 mu M of H2O2. [GRAPHICS] .