Biosensor is developed for detecting the marker of brain fag-amylase.Ferrocene

as the electron transfer

is immobilized by Nafion.Glucose oxidase（GOD）and α-glucosidase（GA）are linkes on the Nafion-ferrocene modified glassy carbon electrode by gelatin embedment. The results show that the biosensor displays a good specificity

sensibility and accuracy.The current of the biosensor has a linear relationship with the concentration of amylase about 50～820U/L.The detection limit is 17.5U/L and response time achieved 95% steady state is no more than 30s.The biosensor response is investigated in terms of pH

temperature and etc.The biosensor is applied for direct measurements of amylase in saliva of human

and satisfactory result is got.