The metal core piezoelectric fiber (MPF) is one of the new type piezoelectric devices for sensors and actuators. When an external harmonically varying voltage is applied on the electrodes of a cantilevered MPF, it will cause longitudinal vibration. The equal external force can be driven from the strain in the piezoelectric elements that caused by the electric field. Using the vibration theory of a cantilevered bar, the longitudinal vibration equations can be given for the MPF as a cantilevered bar. The electric displacement can be derived by the constitutive equations for the piezoelectric element. And the electric charges on the electrodes can be driven by integrated over the surface of electric displacement. The total current flowing into the electrode surface and the admittance of the MPF can be derived from the electric charge. Using the resonance frequency, the elastic coefficient at a constant electric field can be driven from the admittance. And using the antiresonance frequency, one can get the electromechanical coupling factor . The dielectric permittivity at a constant stress can be extracted by the lower capacitance. Using above parameters, the piezoelectric coefficients can be calculated. One experiment was performed. The theoretical simulations and experimental results show that this method is accurate and available to measure the properties of MPF.