The invention provides a method for measuring a periodic error of a photoelectric range finder. The method comprises the following steps of setting two ranging prisms and a photoelectric range finder,keeping the relative positions of the two ranging prisms unchanged and the centers of the respective devices in equal height and common line, moving the photoelectric range finder and performing distance measurement on the two ranging prisms at each position, calculating the results of multiple distance measurement to solve the periodic error amplitude and the initial phase angle of the photoelectric range finder, and giving a standard deviation of the corresponding measurement. The method, without relying on a length standard device, uses a forced centering device and the ranging prisms to measure and calculate the related parameters of the periodic error amplitude and the initial phase angle, and the manual detection workload is small. The method does not require high measurement environment, has no need to meet harsh use conditions of auxiliary measuring equipment such as a standard steel tape, a grating ruler and a laser interferometer, and can eliminate the influence of linear errors on the measurement result, improve the reliability of the measurement result, and represent the measurement accuracy level by measuring the standard deviation.