A palladium/graphitic carbon nitride(g-C3N4)-single walled carbon nanotubes(SWCNTs) composite sensor was constructed for the detection of estradiol(E2).Firstly,the g C3N4- SWCNTs were synthesized via solid grinding and followed by thermal polymerization with melamine(MAM) and single walled carbon nanotube(SWCNTs) as precursors,then Pd nanoparticles were loaded on the as prepared nanocomposite by self-assembly method.The morphology and composition of the Pd/g-C3N4-SWCNTs material were characterized by SEM,TEM,XRD and FTIR techniques,and its electrocatalytic performance toward estradiol(E2) was investigated by cyclic voltammetry.The Pd/g-C3N4-CNTs nanocomposite sensor was used for the detection of E2 in feedstuff sample.Under the optimum conditions,the DPV current response for E2 increased linearly in the concentration range of 5-150 μmol/L with a linear equation of Ipa(μA)=0.834 7+0.007 0CE2(r=0.990) and a detection limit(LOD,S/N=3) of 1.7 μmol/L.With good stability and selectivity,and no significant difference with the HPLC method,this method could meet the requirements for detection of E2 in feed samples.