In this paper a nanocomposite prepared by graphene (GR) and SnO2 nanosheets was used to modify a N-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode. The presence of GR–SnO2 nanocomposite on the electrode surface exhibited synergistic effects to improve the electrochemical performance of the modified electrode. Electrochemical behaviors of dopamine (DA) on the electrode were evaluated by cyclic voltammetry and differential pulse voltammetry. The results indicated that the GR–SnO2 nanocomposite modified electrode displayed high electrocatalytic activity to the oxidation of DA with the increase of the redox peak currents and the decrease of the peak-to-peak separation. Under the selected conditions the oxidation peak current was proportional to the DA concentration in the range from 0.5 to 500.0μmol/L with a detection limit of 0.13μmol/L (S/N=3). The modified electrode showed excellent selectivity and sensitivity even in the presence of high concentration of uric acid. The proposed method was applied to determine DA content in real samples with satisfactory results.