A moderate and simple in-situ growth approach was adpoted to bond coppernanoparticles noncovalently to graphene for preparation of CuNPs/PAA/GR nanocomposites which were used for electrocatalysis of ractopamine（RAC）.The morphology of the material was observed by scanning electron microscopy（SEM）,and the state of the modified glassy carbon electrode was investigated by electrochemical impedance（EIS）.Tests at various scan rates and pH conditions indicated that the modified electrode has an adsorption-controlled electrochemical system.The mechanism for the electrode reaction for ractopamine involves a two-electron transter process accompanied by a deprotonation step.Electrochemical parameters were calculated as follows:the electron transfer number（n） was 1.7,the effective area for the CuNPs/PAA/GR/GCE electrode was 3.57 cm2,12.6 times as large as bare electrode,and the adsorption capacity（Гs） value was 1.98×10-12 mol/cm2.Under the optimal conditions by differential pulse voltammetric measurement,the calibration curve of RAC was linear in the range of 1-30 μmol/L（r2=0.990 2） with a detection limit（S/N=3） of 18.3 nmol/L.With advantages of facile fabrication,high sensitivity,good stability and high reproducibility,the sensor was applied in the detection of ractopamine in pork samples with recoveries of 97.0%-102.5% and relative standard deviations（RSD） of 2.8%-3.2%.