The beam path of Michelson interferometer was adjusted to make sure that the responsive voltage rates of the photoelectric probe was consistent with that of the triangular wave slaving voltage, and to keep maximum peak to peak value. By continuously changing the slaving voltage, the related changes in responsive voltage and extension offset. dependence on driven voltage was find. When measuring the harmonic response features, peak to peak value rates of responsive voltage and that of extension offset are used and compared.