In this paper, we propose a channel estimation method using time domain training sequences. Most recent works generally use a correlation scheme for channel estimation in OFDM systems with time domain sequences. However, the performance of this method is affected dramatically by the correlation characteristics and suffers from multipath interference. Rather than correlation analysis, we provide a new method based on least mean square (LMS) theory. The selection of parameter and corresponding schemes in time-varying channels as well as multipath channels with long time delay spreads are discussed too. Simulations of the new scheme and comparisons show its superiority over the conventional method.