Abstract: ZnO nano-clusters and Au nano-particles were prepared and dispersed in chitosan, which was dropped on the surface of glassy carbon electrode, to form the composite film modified GCE electrode or named abbreviately as Au-ZnO-CHIT/GCE. The electrochemical property of the modified electrode was studied by cyclic voltammetry. It was found that morphine showed an oxidation peak, based on this finding, a selective method for determination of morphine by differential pulse voltammetry was proposed. Linear relationship between values of peak current and concentration of morphine was ranged from 5.3×10-6 to 6.5×10-4mol·L-1, with detection limit (3S/N) of 1.8×10-6mol·L-1. The proposed method was used in the determination of morphine in urine, giving values of recovery in the range of 80.0%-99.6%.