Abstract: AIM　To study the determination of dopamine (DA) in the presence of ascorbic acid (AA) using poly(4-aminopyridine) (POAP) film modified electrode. METHODS　The POAP modified electrode was polymerized on a glassy carbon electrode by cyclic voltammetry, and the quantitative determination of DA was by 2.5th-order differential electrochemical method. RESULTS　The POAP electrode showed molecular recognition and electrocatalysis characteristics, DA showed a very sensitive response at the electrode. DA could be determined in the presence of 2000-fold of AA without obvious interference. The detection limit was 42×10^-11 mol.L^-1 with 8 min accumulation. CONCLUSION　The useful life period of the modified electrode was three months at least. The anodic peaks of DA and AA could be separated by about 200 mV at this electrode. POAP electrode could be used for the determination of neurotransmitter DA in the presence of plenty of AA.