A method for controlling a phase delay offset point of a modulator, comprising: acquiring backlight detection current signals output from the modulator in different working states, and determining harmonic amplitude values of the backlight detection current signals corresponding to the different working states; determining a detection value of the phase delay offset point corresponding to the modulator according to the determined harmonic amplitude values; and comparing the detection value with a set target value of the phase delay offset point, and controlling a position of the phase delay offset point corresponding to the modulator according to a comparison result; characterized in that the different working states respectively are: a state in which no pilot signal is input to the modulator; and a state in which two different phase shift pilot signals are time-sharing superposed to the modulator; the harmonic amplitude values of the backlight detection current signals corresponding to the different working states are determined through the following formula: | E out | 2 = | E i | 2 4 [ sin 2 π V d, I + V b, I 2 V π, I + sin 2 π V d, Q + V b, Q 2 V π, Q − 2 sin π V d, I + V b, I 2 V π, I sin π V d, Q + V b, Q 2 V π, Q cos 2 φ IQ + k cos ωt + θ] wherein V d,I, V π,I, V b, I respectively refer to a modulation amplitude, V π voltage and an offset voltage of an I-path of the modulator, and are respectively set by a system; V d,Q, V π, Q, V b, Q respectively refer to a modulation amplitude, V π voltage and an offset voltage of a Q-path of the modulator, and are respectively set by the system; 2 φ IQ refers to a detection value of the phase delay offset point; when the corresponding working state is the state in which no pilot signal is input to the modulator, ω =0, θ =0; when the corresponding working state is the state in which the two different phase shift pilot signals are time-sharing superposed to the modulator, ω ≠0. acquiring backlight detection current signals output from the modulator in different working states, and determining harmonic amplitude values of the backlight detection current signals corresponding to the different working states; determining a detection value of the phase delay offset point corresponding to the modulator according to the determined harmonic amplitude values; and comparing the detection value with a set target value of the phase delay offset point, and controlling a position of the phase delay offset point corresponding to the modulator according to a comparison result; characterized in that the different working states respectively are: a state in which no pilot signal is input to the modulator; and a state in which two different phase shift pilot signals are time-sharing superposed to the modulator; the harmonic amplitude values of the backlight detection current signals corresponding to the different working states are determined through the following formula: | E out | 2 = | E i | 2 4 [ sin 2 π V d, I + V b, I 2 V π, I + sin 2 π V d, Q + V b, Q 2 V π, Q − 2 sin π V d, I + V b, I 2 V π, I sin π V d, Q + V b, Q 2 V π, Q cos 2 φ IQ + k cos ωt + θ] wherein V d,I, V π,I, V b, I respectively refer to a modulation amplitude, V π voltage and an offset voltage of an I-path of the modulator, and are respectively set by a system; V d,Q, V π, Q, V b, Q respectively refer to a modulation amplitude, V π voltage and an offset voltage of a Q-path of the modulator, and are respectively set by the system; 2 φ IQ refers to a detection value of the phase delay offset point; when the corresponding working state is the state in which no pilot signal is input to the modulator, ω =0, θ =0; when the corresponding working state is the state in which the two different phase shift pilot signals are time-sharing superposed to the modulator, ω ≠0. V d,I, V π,I, V b, I respectively refer to a modulation amplitude, V π voltage and an offset voltage of an I-path of the modulator, and are respectively set by a system; V d,Q, V π, Q, V b, Q respectively refer to a modulation amplitude, V π voltage and an offset voltage of a Q-path of the modulator, and are respectively set by the system; 2 φ IQ refers to a detection value of the phase delay offset point; when the corresponding working state is the state in which no pilot signal is input to the modulator, ω =0, θ =0; when the corresponding working state is the state in which the two different phase shift pilot signals are time-sharing superposed to the modulator, ω ≠0.