Flicker, defined as unnatural temporal fluctuations in perceived image intensity, is a common artifact in old films. Flicker removal is needed due to the high quality requirement of revitalizing old films. In this paper, we propose a least square estimation (LSE) method for eliminating flicker in film archives. The essential point of this method is to estimate flicker parameters for each small region by minimizing the squared error between corrected intensities in previous frames and estimated intensities in current frame. Based on the thresholds of flicker parameters, stationary and motion blocks are detected. For those stationary blocks, a criterion of mean squared error (MSE) is added to strongly restrict the stationary area. These blocks, in which MSEs surpass the threshold, are flagged as motion blocks. Flicker parameters in motion blocks are retrieved by iterative interpolation process. Synthetic and real flicker image sequences are used to evaluate and demonstrate the algorithm's usefulness in terms of average PSNR and visual quality in real-time playback respectively. Moreover, the results gotten from LSE method were compared with those obtained from Roosmalen method. The results of LSE method show an impressive improvement on PSNR in simulated flicker sequence. Meanwhile, no blocky effect and no new artifacts introduced are visible in real-time play back for both synthetic and real sequence.