The invention is a feedback control module in self-adapting polarization mode dispersion compensator, comprising; an electric low-pass filter, used to filter high-frequency noise, band width of the filter is required to match the sampling frequency of a four-channel synchronous collecting card; the four-channel synchronous collecting card and multichannel D/A converter and digital filter, used to make matrix transformation on the four-channel digital voltage signals obtained by sampling to obtain polarization degree value of chain circuit and filter noise by digital median filter; calculation control device, using a control algorithm to optimize and regulate the voltages of two electric controlled polarization controllers of a mode dispersion compensator, thus making polarization degree of optical signals in an optical fiber chain circuit reach maximum and implementing self-adapting compensation; it provides feedback signals for a polarization mode dispersion compensator, and by searching and tracking the control algorithm, in time, fast and effectively compensates and tracks random varying polarization mode dispersion.