In this work,Ag nanoparticles/multi walled carbon nanotubes(AgNPs/MWCNTs) composites were synthesized with multi walled carbon nanotubes(MWCNTs) and silver nitrate as raw materials,and sodium borohydride as reduction agent,and the AgNPs/MWCNTs composites were characterized by ultraviolet visible absorption spectroscopy,infrared spectroscopy,Raman spectroscopy and X-ray diffraction.Based on this,an Ag nanoparticles/multi walled carbon nanotubes modified electrode(AgNPs/MWCNTs/GCE) was prepared by immobilizing AgNPs/MWCNTs onto the surface of glassy carbon electrode.Effects of buffer solution,pH value，supporting electrolyte and scanning rate on electrochemical reactivity of the AgNPs/MWCNTs/GCE were investigated.Results showed that the nanocomposite modified electrode had a better electrocatalytic activity for sulfamethoxazole(SMZ),compared with MWCNTs or Ag nanoparticles modified electrode.Under the optimized conditions,there was a linear relationship between SMZ and peak current in the range of 3.0×10-7-5.0×10-5 mol/L,and the limit of detection(S/N=3) was 6.4×10-8 mol/L.The method is simple and rapid,and could be used for the detection of SMZ in river samples.