Based on the analysis of the performance of Boumard’s SNR method for wireless orthogonal frequency division multiplexing (OFDM) systems, a new estimation al-gorithm of the noise variance is proposed by only using the data samples of the two training symbols in the preamble, and the second order moment of these data samples is employed to estimate the signal power. The average SNR and the SNRs on the subchannels can all be estimated by the proposed algorithm, and its per-formance is independent of the channel’s frequency selectivity. Simulation results show that the performance of the proposed method is highly improved and much better than that of Boumard’s method. Based on the analysis of the performance of Boumard’s SNR method for wireless orthogonal frequency division multiplexing (OFDM) systems, a new estimation al-gorithm of the noise variance is proposed by only using the data samples of the two training symbols in the preamble, and the second order moment of these data samples is employed to estimate the signal power. The average SNR and the SNRs on the subchannels can all be estimated by the proposed algorithm, and its per-formance is independent of the channel’s frequency selectivity. Simulation results show that the performance of the proposed method is highly improved and much better than that of Boumard’s method.