A method for modulating an orthogonal frequency division multiplexing optical signal, wherein the method comprises: • performing bit-to-symbol mapping on a baseband signal to obtain a symbol sequence of the baseband signal (steps 101, 201); • performing serial-to-parallel conversion on the symbol sequence to obtain at least two sub symbol sequences of the baseband signal, wherein each sub symbol sequence of the baseband signal corresponds to a subcarrier of an orthogonal frequency division multiplexing, OFDM, signal (steps 102, 202); • determining, from all subcarriers of the OFDM signal, a subcarrier used for loading a pilot signal, wherein a first sub symbol sequence of the at least two sub symbol sequences of the baseband signal corresponds to the determined subcarrier (steps 103, 204); • determining a symbol sequence of the pilot signal according to information of the pilot signal, a frequency of the pilot signal according to the information of the pilot signal, and determining a frequency of the determined subcarrier used for loading the pilot signal (step 901); • if the frequency of the pilot signal is higher than the frequency of the determined subcarrier used for loading the pilot signal, determining a symbol sequence obtained by performing Hilbert transform on the pilot signal as a symbol sequence of the pilot signal, wherein the symbol sequence of the pilot signal is a discrete periodic sequence (step 904); • if the frequency of the pilot signal is lower than the frequency of the subcarrier used for loading the pilot signal, determining a conjugate sequence of the symbol sequence obtained by performing the Hilbert transform on the pilot signal as the symbol sequence of the pilot signal (step 905); • if the frequency of the pilot signal is equal to the frequency of the subcarrier used for loading the pilot signal, determining a preset constant sequence as the symbol sequence of the pilot signal (step 906); • replacing the first sub symbol sequence of the baseband signal with the symbol sequence of the pilot signal, or superimposing the symbol sequence of the pilot signal on the first sub symbol sequence of the baseband signal (steps 104, 205); and • performing inverse discrete Fourier transform, parallel-to-serial conversion, digital-to-analog conversion, and electrical amplification processing on content currently corresponding to all the subcarriers of the OFDM signal, thereby arriving at processed data, and modulating a light wave comprising all subcarriers by using the processed data and a bias electrical signal, to form an OFDM optical signal loaded with the pilot signal (steps 105, 206). • performing bit-to-symbol mapping on a baseband signal to obtain a symbol sequence of the baseband signal (steps 101, 201); • performing serial-to-parallel conversion on the symbol sequence to obtain at least two sub symbol sequences of the baseband signal, wherein each sub symbol sequence of the baseband signal corresponds to a subcarrier of an orthogonal frequency division multiplexing, OFDM, signal (steps 102, 202); • determining, from all subcarriers of the OFDM signal, a subcarrier used for loading a pilot signal, wherein a first sub symbol sequence of the at least two sub symbol sequences of the baseband signal corresponds to the determined subcarrier (steps 103, 204); • determining a symbol sequence of the pilot signal according to information of the pilot signal, a frequency of the pilot signal according to the information of the pilot signal, and determining a frequency of the determined subcarrier used for loading the pilot signal (step 901); • if the frequency of the pilot signal is higher than the frequency of the determined subcarrier used for loading the pilot signal, determining a symbol sequence obtained by performing Hilbert transform on the pilot signal as a symbol sequence of the pilot signal, wherein the symbol sequence of the pilot signal is a discrete periodic sequence (step 904); • if the frequency of the pilot signal is lower than the frequency of the subcarrier used for loading the pilot signal, determining a conjugate sequence of the symbol sequence obtained by performing the Hilbert transform on the pilot signal as the symbol sequence of the pilot signal (step 905); • if the frequency of the pilot signal is equal to the frequency of the subcarrier used for loading the pilot signal, determining a preset constant sequence as the symbol sequence of the pilot signal (step 906); • replacing the first sub symbol sequence of the baseband signal with the symbol sequence of the pilot signal, or superimposing the symbol sequence of the pilot signal on the first sub symbol sequence of the baseband signal (steps 104, 205); and • performing inverse discrete Fourier transform, parallel-to-serial conversion, digital-to-analog conversion, and electrical amplification processing on content currently corresponding to all the subcarriers of the OFDM signal, thereby arriving at processed data, and modulating a light wave comprising all subcarriers by using the processed data and a bias electrical signal, to form an OFDM optical signal loaded with the pilot signal (steps 105, 206).