In this study, a modified two-dimensional axisymmetric finite element model is used to analyze the deflections of the piezoelectric actuator of valveless micropump after being driven by applied voltage. And the volume change of the pump chamber caused by the deformation of the piezoelectric actuator is calculated. We expect these analyses will help the design of piezoelectric valveless micropump. This model is able to analyze the piezoelectric materials which can transform the mechanical energy to electric energy and vice versa by properly assuming the three displacement fields and including the electrical potential as the fourth degree of freedom. Comparisons of some examples are made between the present work and those available in the literature to validate the exactitude and the feasibility of the present work. Furthermore, the inspections of the variations of the deflections will be carried out by changing the geometrical dimensions of the piezoelectric actuators under the same driven voltage.