Comparing different frequency measurement methods of vibrating beam component(VBC) a non-contact instantly excited technique of frequency measurement of VBC using diffused reflection optical triangulation is developed.In order to avoid the interactions between displacement and rotation of VBC during measurement,diffused reflection optical triangulation is applied to measure the displacement of VBC.Moreover,instantly excited method is used to eliminate environment noise caused by conventional harmonic vibration method.At last,maximum likelihood estimation(MLE) method is used to solve the model of instantly excited frequency measurement method.The experimental results show that,in normal conditions,the frequency measurement accuracy of instantly excited method is 50 times higher than that of harmonic vibration method.It reaches 0.006 Hz.