Abstract: The sinusoidally excited vibration of bonding tool at measurement for a ultrasonic load was measured by continuously scanning laser Doppler vibrometer PSV-400-M2(1.5 MHz).The experimental phenomena and scanning testing results showed the steady-state vibration show uncertainty when the tightness changes; under the same tightness there is single-node in vibration, but under different tightness the node positions have changed;the velocity amplitude is not as the largest as expection.In addition, the mathematics modeling was carried out based on the vibration theory of flexible beam.