π-rotation low-density parity-check (LDPC) code is applied in polarization division multiplexing differential quadrature phase shift keying (PDM-DQPSK) modulation optical fiber communication system. Performance analysis and comparison are conducted by numerical simulation, in which the same kind of codes with higher code rates are generated by employing puncturing technique and compared with primitive code in correction performance. With regard to decoding, the Chi-square statistical model of PDM-DQPSK is derived and compared with Gaussian one. The results exhibit that π-rotation LDPC codes can achieve their utmost performances when code rate is 0.5 and Chi-square statistical model is employed, which ensures bit error rate (BER) is below 10-9 while optical signal to noise ratio (OSNR) is 14.2 dB. When OSNR penalty is 2 dB, the system can tolerate 102 ps/nm chromatic dispersion, 18 ps first-order polarization mode dispersion and 4.88×10-2 rad nonlinear phase shift. The results indicate that π-rotation LDPC codes can enhance the transmitting reliability significantly.