The disclosure discloses a method and an apparatus for determining a bias point of a modulator, wherein the method includes: adding pilot signals to the bias voltages of the modulator; adjusting the bias point of the modulator at a predetermined step and acquiring a first harmonic amplitude value corresponding to each bias point in a backlight detection current signal output by the modulator; and determining a bias point corresponding to the maximum value of the first harmonic amplitude values associated with multiple bias points as the bias point of the modulator. By virtue of the disclosure, the detection of a difference frequency signal can be eliminated, thereby reducing the complexity and cost of a periphery control circuit while ensuring the control accuracy, effectively improving the stability and reliability of the control process, and improving the modulation and transmission performance of optical signals in the whole system.