In order to investigate blast strain wave signal characteristic, in this paper, Hilbert-Huang Transform (HHT) is applied to analyzing the time-frequency spectrum of blast strain wave signal. Empirical mode decomposition and Hilbert spectral analysis for blast strain waves signal are discussed. Comparison between HHT and STFT of blast wave signal are analyzed. Multiple frequency interaction of blast wave signal in air and rock is discussed by numerical simulation, and also confirmed the signal characteristic by dynamic photo-elasticity experiment. It is demonstrated that blast strain wave main frequency within the scope of few hundred kHz to few megahertz in adjacent field to a borehole. HHT method may be apparent in the details of the explosion strain wave propagation characteristics. The blast strain wave profile is caused by different frequency wave dynamics interaction.