In order to study the effect of photodetector reverse bias voltage on visibility measurement, a photodetector was used to detect the stable pulse beam, the reverse bias voltage of the photodetector was changed, and the response time and root mean square (RMS) of the output signal were read with the oscilloscope observing photodetector output signal waveform. The results show that the drift of the reverse bias voltage causes the photodetector response time changing, and RMS of the photodetector output signal is affected. The drift can affect the uncertainty of visibility measurement. When choosing photodetector in the designing of visibility meter, the influence of the reverse bias voltage should be considered, and the reverse bias voltage must be stable.