An average-minimum mean squared error (A-MMSE) channel estimation algorithm is proposed to address the problem of a high bit error ratio (BER) of the minimum mean squared error (MMSE) channel estimation algorithm in orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithm first constructs a new pilot structure based on the 802.11n standard. Then, downsampling and oversampling processes are performed at the receiver and transmitter, respectively. Finally, the channel frequency response is obtained using the known training sequences and pilots. The simulation results indicate that, compared with the traditional MMSE algorithm, the proposed A-MMSE channel estimation algorithm improves the signal-to-noise ratio by approximately 8dB at a BER of 10-3. Therefore, the proposed channel estimation algorithm notably improves the BER performance of the system.