A new method for the frequency identification of rotating machinery blade vibration at even speed is presented. The vibration signal is obtained by the method of Blade Tip-Timing and is a Sub- Nyquist sampling data with multiple harmonics. With the analysis of signal’s mathematical model, the frequencies are identified based on ESPRIT through two Blade Tip-timing sensors which are working as delay and non-delay signal channels. The theoretic foundation of ESPRIT and the process for the frequencies estimation are introduced combining with the computer simulation and practical experimentation, which are used for testing and verifying the performance of this new method in practice.