Facing the application scene which is hard to obtain the offset working point information from signal light, a kind of repetition-frequency optical shaping scheme with reference light is proposed after analyzing the output performance of different wavelengths of signal light passing through the intensity modulator. The wavelength division multiplexer is used to import and separate the reference light. Benefited from the relevance of output laser of different wavelengths passing through the intensity modulator, it is possible to obtain the offset working point information of signal light based on the intensity of reference wave. It is possible to obtain the offset working point information effectively in the scheme and is not effected by signal light change.