The [Os(bpy)2(PVP)10Cl]Cl polymer and Nafion have been covered on a glassy carbon electrode by drop-coating to fabricatea double-layer membrane modifed electrode. The modifed electrode showed an excellent electrocatalytical activity for theoxidation of the neurotransmitter epinephrine (EP). Under usual physiological pH conditions, the logarithm of the catalyticcurrent of EP vs. its concentration showed a linear relation in the range of 4.0×10－9－5.4×10－6M and 5.4×10－6－3.1 10×4M with correlation coeffcient of 0.995 and 0.996, respectively. The modifed electrode could eliminate effcientlythe interference of ascorbic acid, glucose and uric acid at 200-, 8600-and 20-fold concentration of EP (at 5.0×10－5M), and ithas been satisfactorily used for the amperometric determination of EP. The electrocatalytical rate constant kch was evaluatedwith a rotating disk electrode. Both the presence of a Nafion folm and the increase in EP concentration resulted in a decrease ofkch. The apparent Michaelis±Menten constant is about 0.51 mM. The modi®ed electrodes exhibited a good reproducibility,sensitivity and stability for the determination of EP.