With the increase of nonlinear loads in power system, power quality problems caused by transient voltage disturbance is more and more serious, the detection of transient voltage disturbance signal becomes the key to improve power quality. This paper proposes a transient voltage disturbance detection method based on Ensemble-Kalman filtering, the elements of Ensemble-Kalman filtering’s background ensemble are reformed according to the characteristics of transient voltage disturbance. The modified values of voltage state at k – 1 and k - 2 form the background ensemble, then the real-time voltage’s amplitude is obtained by recursive computation, thus the beginning and ending times of transient disturbances are positioned and abrupt amplitude is traced out. Simulation results show that the proposed method can quickly detect voltage’s sag/swell, precisely position the beginning and ending times of transient voltage disturbance, and track down the abrupt amplitude. The proposed method is more effective than the traditional Kalman filter (KF) and root-mean-square (RMS) algorithm.