In this paper, we propose a channel estimation method associated with the interpolation order for DVB-T systems. We first analyze the time varying channel and frequency selective channels, and then derive the channel index which indicates the ratio of the time and the frequency axis variation. This channel index is used for determining the order of interpolation such as time axis followed by frequency axis interpolation or vice versa. The computer simulation shows that the proposed method can provide more accurate channel information, thereby improving the overall channel equalizing performance.