A graphene-chitosan modified glassy carbon electrode was prepared. Electrical conductivity of the modified glassy carbon electrode( GCE) was investigated by cyclic voltammetry( CV). Competitiveelectrochemical immunoassay was performed to detect diethylstilbestrol by differential pulse voltammetry( DPV). Under the optimized conditions,the Δ-value of oxidation peak current was proportional to diethylstilbestrol concentration in the range between 1 and 2 500 μg / L. The linear equation was ΔI =25. 036 8 + 0. 0...