PEG modified Fe3O4 nanoparticles synthesized by coprecipitation were dispersed in sodium dodecylbenzenesulfonate(SDBS) solution and modified on the surface of magnetic carbon paste electrode(MCPE) to prepare the SDBS-PEG-Fe3O4/MCPE.Cyclic voltammetry(CV) showed that the modified electrode exhibited a strong catalytic effect on the electrochemical oxidation of dopamine(DA).The oxidation peak current on the modified electrode was 5 times higher than that on the bare MCPE.The potential difference between oxidation peak and reduction peak decreased from 0221 V to 0.044 V,which indicated the increase of redox reversibility of DA.Square wave voltammetry(SWV) showed that the oxidation peak current had a linear relationship with concentration of DA in the ranges of 5.0×10-7-2.0×10-5 mol/L and 2.0×10-5-1.0×10-4 mol/L.The detection limit(S/N=3) was 1.4×10-7 mol/L.The interference of ascorbic acid(AA) and uric acid(UA) could be eliminated efficiently.The proposed method was used to detect the dopamine hydrochloride injection with satisfactory results.