The mechanical mode of an Half coated Metal core Piezoelectric Fiber (HMPF) actuator is established. According to the constitutive piezoelectric equations, the analytical expressions of the tip deflection, blocking force and the natural frequencies are derived. The effect of the metal core on those properties of HMPF actuator is investigated based on the numerical results of the equations and FEM. The experimental results indicate that the maximum tip deflection of cantilevered HMPF, maximum blocking force and the first resonance frequency are 589 μm,427 μN and 28 Hz,respectively, FEM results are coincident with theoretical values on the whole. The results show that the actuator can give a big deflection, a small block force, and a low resonance frequency.