Based on EulerBernoulli beam theory, the voltage response of the cantilevered piezoelectric beam for bimorphs in series connection with aluminum substrates and the resonance frequency shift of shortopen circuit are investigated in this paper. By using the total thickness of the cantilevered beam and the thickness of piezoelectric ceramics are chosen as the influencing parameters，the single/multimode solutions of the output voltage are derived firstly, then the shortopen circuit resonance frequency shift under different thickness of the cantilevered piezoelectric beams is analyzed on the basis of the singlemode solutions. The results exhibit that the singlemode solutions are of good estimation and simple calculating comparing with the more accurate multimode solutions; in the arbitrary range of variable load resistance, there exists the worst point of the thickness of piezoelectric ceramics, which leads to maximum resonance frequency shift. Accordingly, the worst point should be avoided for optimum adaptability and more desirable efficiency of energy harvesting when the cantilevered piezoelectric beam is designed.