In this paper, a principle of polarization diversity receiver for coherent optical fiber communication is briefly discussed, and the polarization-insensitive receiver on basis of polarization diversity is achieved for the first time in China. Good demodulated signals independent on polarization are obtained at 137.2 MHz and 146.0 MHz of sinusoidal-wave. This method is being applied to a 140 MBit/s FSK coherent fiber communication system at 1.5 nm.