Abstract: The effect of electric load on the piezoelectric vibrational system due to electroacoustic coupling was analytically investigated. The analytical results shown that: （1） when load impedance continually changes from -∞ to+∞, the mechanical resonant frequency of the system would fill all frequency domain from 0 to ∞; （2） the displacement and stress distributions also would change, even the displacement may be zero at both free ends （i.e. at points where stress is equal to zero）.
Finally, the experiments for longitudinal vibration of piezoelectric strip of lateral polarization were given and compared with theoretical results.