Abstract: In high power condition, not only the linewidth of single frequency fiber laser becomes wider greatly, but also its frequency stability becomes worse because of effects of many factors. PDH frequency stabilization technology can be applied in high-power condition with high frequency stability. To realize stable output of high power 1 064 nm single frequency fiber laser, the principle of PDH frequency stabilization technology was analyzed and a PDH optical heterodyne frequency stabilization system was established. It is found that the key of the PDH system is the detection of 100 MHz phase modulation optical heterodyne signal. Firstly, the optical signal was detected and amplified by Si detector with self-designed preamplifier circuit. Secondly, demodulation circuit was designed and the amplified signal and a reference signal were mixed together with a mixer to realize demodulation, as a result, the frequency discrimination curve was obtained. This indicates that the detection of the optical heterodyne signal has been realized.