In the letter the influence of input polarization on the fringe visibility and phase in fiberMach-Zehnder interferometer is described, an verification experiment is carried on. In the experiment, a PZT acting as phase-modula-tion is joined in an arm of interferometer, the change ofwaveform is observed due to different input polarization by os-cillograph. The change of waveform is in accordance with the theory analysis. The result of experiment verify the in-fluence of input polarization on visibility and phase.