Abstract: In this paper, a low-complexity Kalman filter algorithm in the short-time Fourier transform (STFT) domain is proposed for acoustic echo cancellation. The observation equation is obtained based on the convolutive transfer function in the STFT domain, and the echo path in the frequency domain is modeled by using the first-order Markov process. The exact Kalman filter is derived, and the estimation of the process noise and observation noise is discussed. A fast implementation method is presented to reduce the complexity of the exact Kalman filter. In addition, more adjacent frequency points of the far-end signal are introduced to further improve the echo cancellation performance. Experimental results show that the proposed algorithm is insensitive to the near-end interference and unnecessary to have an explicit double-talk detection algorithm, and it converges faster than the frequency domain adaptive filtering algorithm.