Blade tip clearance (BTC) and blade vibration measuring are the principal tools for blade health monitoring (BHM), which can improve the efficiency and reliability of turbomachinery. In this paper, a BTC monitoring method based on pulse-trigger of eddy current sensor (ECS) is presented, in the light of the sub-Nyquist sampling caused by the limit of narrow-band, especially for the high linear velocity. The proposed method optimizes the static radial and circumferential calibration technology to obtain the sensitivity of ECS in the different relative location against the tip of blade and to obtain the function of impedance of the ECS that relates to the distance and the contact ratio of the ECS from the tip of blade. Combining blade tip timing (BTT) technology into BTC monitoring, this method calculated the contact ratio of the ECS from the blade, in order to obtain the accurate clearance depends on the function obtained before for all sampling points. Also, a BTC monitoring rig is established to validate the feasibility of this method under varying rotating speed. The results show that this method can solve the problem of sub Nyquist sampling caused by the limit of narrow band for ECS in the condition of high linear velocity. Compared with the location obtained by peak picking, the method presented in this paper can significantly improve the accuracy of BTC monitoring. This research can provide the basis for BTC active control and BHM based on ECS.