Using adenosine-5'-monophosphate (5'-AMP) as a substrate, the surface acoustic wave (SAW)-impedance sensor has been successfully applied to detection of acid phosphatase and microanalysis of Cu2+ and Ag+. The assay of acid phosphatase is based on the change in conductance of the solution caused by enzymatic reaction between 5'-AMP and acid phosphatase. The microanalysis of Cu2+ and Ag+ is based on its inhibitory action on enzyme. The Michaelis constant and the corresponding maximum initial rate are estimated to be 4.49 × 10-3 mol l-1 and 8,841 Hz min-1, respectively, at pH 4.5 and 28°C. The recovery of the sensor system ranges from 97.9-107.0% (n = 6). The experimental detection limit of enzyme is 0.7 mU ml-1. The inhibition of Cu2+ and Ag+ is a noncompetitive one. The possible inhibition mechanism is discussed. The kinetic parameters and inhibition parameters are estimated. The detection limits of Cu2+ and Ag+ is 7.6 × 10-7 and 2.0 × 10-8 . Some factors such as temperature, pH value, and active energy are also discussed.