To avoid the limitation of Polarization Mode Dispersion (PMD) to the long-distance and high-rate optical fiber communication system,a dynamic adaptive PMD compensation system based on Degree of Polarization (DOP) was designed. According to the relationship between DOP and Differential Group Delay (DGD),the optimum value was searched and tracked by the control algorithm,and the value of PMD and its compensation effect could be reflected by DOP. Through adjusting the angle of waveplates in the polarization controller and the length of the variable delay line,the two principal states of polarization were adjusted to optimize DOP,and a close-loop compensation system was established. It was demonstrated from the experimental results that the worsening signal waveform was resumed effectively,and the opening of the eye diagram was improved obviously. The response time of the compensation system was about 110ms,and the Bit Error Rate (BER) was 3.59e-16,which satisfied the requirement for BER in the transmission system.