The invention relates to a channel estimation method in a power line orthogonal frequency division multiplexing (OFDM) communication system. The channel estimation method comprises a first step of at a sending terminal, modulating information into a frequency domain signal, and converting the frequency domain signal into parallel signals; a second step of inserting a pilot, and converting the frequency domain information into time domain information after inverse fast Fourier transformation (IFFT); a third step of adding a cyclic prefix in the signal subjected to IFFT, so as to eliminate ISI and ICI in the OFDM system, entering a low-voltage power line channel after parallel to serial conversion, and arriving at a signal receiving terminal; a fourth step of removing the cyclic prefix at the receiving terminal, then performing FFT so as to obtain the frequency domain signal; and a fifth step of extracting information in a pilot position in the signal, performing channel estimation on the information, expanding a P-order polynomial to replace an inversion operation in an adopted linear minimum mean squares error (LMMSE) estimation method, and optimizing a coefficient of the polynomial so as to obtain a channel response estimation value in the pilot position. The channel estimation method can estimate a channel response value in the OFDM communication system effectively, improves the estimation accuracy and lowers the calculation complexity.