The aniline solution containing nicotinamide adenine dinucleotide(NAD＋ )was electrolyzed. Polyaniline film with NAD＋ formed on the platinum thin plate. The thickness of the film was controlled by the charge consumed in the electrolysis, which was 0.006 C in this case. This electrode, used as an anode, was immersed in the solution containing aniline. A second film formed on this electrode during the electrolysis. The charge passed during the second electrolysis was 0.016 C. Alcohol dehydrogenase(ADH) was immobilized on the polyaniline film based on the isoelectric point of ADH and the doping principle of conducting polymers. The enzyme electrode has a od bioelectrochemical response to ethanol in the absence of a homogeneous mediator. The optimum pH, apparent Michaelis- Menten constant and optimum temperature of ADH immobilized in polyaniline film are 7.83, 7.5 mmol• dm－ 3, and 30.6 ℃ , respectively. The activation energy of the enzyme- catalyzed reaction is 33.5 kJ• mol－ 1. The response current of the enzyme electrode increases linearly with increasing concentration of ethanol below 2.4 mmol• dm－ 3.This enzyme electrode can be used to determine the concentration of ethanol.