Abstract: A microelectrode modified with polyphenol oxidase was fabricated and used as a biosensor.Electrochemical behavior of dopamine at the electrode was studied.In a phosphate buffer of pH 6.8,linear response of dopamine at the biosensor was obtained in the concentration range of 2.0×10-6-1.0×10-3mol·L-1.Detection limit (3σ) of 6.0×10-7mol·L-1was obtained.The biosensor has been applied to the determination of dopamine in medical injections,giving RSD′s less than 3%,and recoveries in the range from 95%-110%.