The present invention provides a measuring method for prolonging a usage lifetime of a micro biosensor implanted subcutaneously to measure a physiological signal associated with an analyte. The micro biosensor includes a working electrode and a counter electrode, wherein the counter electrode includes silver and a silver halide having an initial amount. The method includes cyclic steps of: applying a measurement voltage to drive the working electrode to measure the physiological signal, where the silver halide is consumed by a specific amount; stopping applying the measurement voltage; and whenever the physiological parameter is obtained, applying a replenishment voltage to drive the counter electrode, thereby the silver halide of a replenishment amount being replenished to the counter electrode, wherein a guarding value of a sum of the replenishment amount and the initial amount subtracting the consumption amount is controlled within a range of the initial amount plus or minus a specific value.