Acetylcholinesterase was immobilized on glass pH electrode using cross-linking agent, and characteristics of the enzyme electrode such as subshate sensitivity, optimum pH, working stability, and inhibitor effect were investigated. The sensitivity for substrate, acatykholine, was increased proportionally as the molar concentration of working buffer was decreased. The enzyme electrode showed linear response for the concentration range from 0.7 mM to 5.0 mM of acetylcholine in 10 mM PBS (pH 7.4). The optimum pH of the AChE electrode was pH 8.0 which is the same as that of soluble enzyme. For the practical use of this enzyme electrode, the operational stability (or reusability) was studied. In addition, it was found that the detection limit of the AChE electrode for paraoxon was 10^(-9) M and the inhibited electrode by paraoxon was reactivated in the presence of 0.5 mM 2-PAM.