Abstract: Aiming at non-stationary broadband characteristics of micro-seismic signals,adopting correlative threshold dependent on the environmental noise variance,an effective de-noising algorithm was established based on intrinsic time-scale decomposition(ITD).Compared with the de-noised signals based on wavelet transform algorithm,denoising waveforms of ITD algorithm which can completely de-noising preserved precisely peak position with the original signals,and the sudden change detail of onset time was reserved exactly,which showed that ITD algorithm may be applied to pick and judge the first arrival of the primary wave accurately.