An ultrasonic signal processing technique is applied to multimode ar r ival time estimation from Lamb waveforms. Compared with fast Fourier transform ( FFT) and wavelet transform (WT) in time and frequency resolutions, HilbertHuan g transform (HHT) can accurately identify the abrupt time of two frequency compon ents in the signal, which demonstrates the superiority of HHT method. The charac teristic of HHT method avails to estimation of arrival times of multiple Lamb wa ve modes. From energytime plot of Lamb waves processed by using HHT, the time o f energy peak equals to the arrival time of each mode. The experimental results agree with the theoretical values to a larger extent.