A new modified electrode(p-PTA/CS-AB/GCE) was prepared with phosphor-tungstic acid,chitosan and acetylene black.The electrochemical behaviors of chloramphenicol(CAP) on p-PTA/CS-AB/GCE were investigated by cyclic voltammetry(CV).The results showed that there was an obvious reduction peak of CAP on the modified electrode in pH 6.0 PBS buffer solution and the reduction peak current was linear to the scan rate in the range of 40-400 mV/s,indicating that the electrode process of CAP was controlled by absorption.The different concentrations of CAP were determined by differential pulse voltammetry,and a good linear relationship was observed between reduction peak current and CAP concentration in the range of 5.0×10-7-1.0×10-4 mol/L.The detection limit(S/N=3) was 5.13 ×10-8 mol/L.The mothed was applied in the determination of CAP in chloramphenicol tablet sample,with relative standard deviation of 14%and recoveries of 97.7%-105.1%.