An OFDM signal demodulation method, comprising the following steps: adding a pre-obtained timing offset estimation value of an OFDM signal demodulation device to the initial position of an OFDM symbol of a received signal to obtain a window deviation value of the OFDM symbol; calculating a frequency domain channel response of an OFDM synchronous symbol, and processing FFT for the frequency domain channel response to obtain a channel response on transform domain; taking at least two segments from the channel response on transform domain and estimating the power of the signals in each segment, wherein the at least two segments comprises a segment comprising the highest number of samples, and other segments in the at least two segments are subsets of the segment comprising the highest number of samples, and then calculating the ratios of the signal power of other segments to the signal power of the segment comprising the highest number of samples; comparing each of the ratios with a corresponding preset detection threshold in turn, and regarding the segment corresponding to the ratio as a channel time delay extension when the ratio is greater than the corresponding detection threshold; calculating a combined OFDM signal value z ( n) by using the following formulas: z n = x d d + n, n = 0,1, ⋯, N − N cp + d c − 1; z ( n) = [ x ( d d + n) + x ( d d + n - N)]/2, n = N - N cp + d c,···,N - 1, where x ( n) is an input signal before combination, and d c is the channel time delay extension, and d d is the window deviation value; processing the Fast Fourier Transform for the combined OFDM signal value to obtain a frequency domain data subcarrier signal; calculating a frequency domain original channel estimation value, processing the channel estimation based on the original channel estimation value phase modification of the OFDM symbol according to the timing offset estimation value, and processing equalization and detection for the frequency domain data subcarrier signal according to the channel estimation result,. adding a pre-obtained timing offset estimation value of an OFDM signal demodulation device to the initial position of an OFDM symbol of a received signal to obtain a window deviation value of the OFDM symbol; calculating a frequency domain channel response of an OFDM synchronous symbol, and processing FFT for the frequency domain channel response to obtain a channel response on transform domain; taking at least two segments from the channel response on transform domain and estimating the power of the signals in each segment, wherein the at least two segments comprises a segment comprising the highest number of samples, and other segments in the at least two segments are subsets of the segment comprising the highest number of samples, and then calculating the ratios of the signal power of other segments to the signal power of the segment comprising the highest number of samples; comparing each of the ratios with a corresponding preset detection threshold in turn, and regarding the segment corresponding to the ratio as a channel time delay extension when the ratio is greater than the corresponding detection threshold; calculating a combined OFDM signal value z ( n) by using the following formulas: z n = x d d + n, n = 0,1, ⋯, N − N cp + d c − 1; z ( n) = [ x ( d d + n) + x ( d d + n - N)]/2, n = N - N cp + d c,···,N - 1, where x ( n) is an input signal before combination, and d c is the channel time delay extension, and d d is the window deviation value; processing the Fast Fourier Transform for the combined OFDM signal value to obtain a frequency domain data subcarrier signal; calculating a frequency domain original channel estimation value, processing the channel estimation based on the original channel estimation value phase modification of the OFDM symbol according to the timing offset estimation value, and processing equalization and detection for the frequency domain data subcarrier signal according to the channel estimation result,.