A poly（methylene blue）/graphene modified glassy carbon electrode（PMB/GH/GCE） was fabricated by electropolymerizing methylene blue on the surface of glassy carbon electrode modified with graphene.The electrochemical behaviors of dopamine（DA） and ascorbic acid（AA） at the prepared electrodes were investigated using cyclic voltammetry（CV） and differential pulse votammetric（DPV） methods.In pH 6.9 phosphate buffer solution（PBS）,the anodic peak potentials of DA and AA were 0.208 V and -0.108 V，respectively.In comparison with poly（methylene blue） modified glassy carbon electrode（PMB/GCE） and graphene modified glassy carbon electrode（GH/GCE）,the composite modified electrode（PMB/GH/GCE） had superior electrocatalytic activity toward the oxidation of DA and AA,with a peak to peak separation up to 316 mV.Studies showed that MB was firmly non-covalent modification of graphene by electropolymerizing method,and created synergistic effect which could improved sensitivity and molecular recognition ability of the modified electrodes and enabled the sensitive and selective detection of DA in the presence of large number of AA.A DPV technique for measurement for DA over the range of 1.00×10-7-5.00×10-3 mol/L was developed in the presence of 1.00×10-3 mol/L AA,with detection limit of 1.00×10-8 mol/L.The modified electrode was applied in the determination of dopamine hydrochloride injection solution with satisfactory result.