Abstract: Thionine and ferrocyanide were modified on carbon paste electrode by CV electro co-polymerization to prepare the modified electrode, which is abbreviated as PTH/［Fe(CN)6］4-/CPE. In comparison with PTH/CPE, a pair of significant oxidation and reduction peaks was observed in the base solution of 4.5 mol·L-1 HOAc solution, which proved that Fe2+ was successfully introduced into the polymeric film. It was found that vitamin B6 exhibited significant electrocatalytic oxidation at this modified electrode. Under the optimized conditions, linear relationship between values of peak current and concentration of VB6 was kept in the range of 3.0×10-5-1.0×10-3mol·L-1 with detection limit (3S/N) of 6.0×10-6mol·L-1. The modified electrode was used in the determination of VB6 in medicines, giving values of recovery and RSD′s (n=6) in the ranges of 94.5%-101% and 1.8%-2.3% respectively.