A new apparatus which detects directly the blood alcohol concentration（BAC）is introduced.This biosensor comprises a screen-printed carbon electrode modified with alcohol dehydrogenase（ADH）

nicotinamide adenine dinucleotide（NAD+） cofactor and Meldola’s blue（MB）adsorbed on nafion film.It is employed for measuring the current which is generated by the electrochemical reaction catalyzed by alcohol dehydrogenase.And a single chip microcomputer

EM78P458

is used as central control unit.It measures the output of current conduced by the biosensor.Then

the detected current is amplified and processed

and the results are displayed on LCD.Experiment results show that the output of apparatus appears good relativity with that from the automatic biochemistry analyzer.A new accurate way for detecting BAC is provided.