The chromatic dispersion and nonlinear performances of 16DPASK modulation format in optical communication are analyzed.Based on the modulation and demodulation principles of this optical signal,the optimal extinction ratio for back-to-back configuration is theoretically derived as 1.43 dB,which is verified by simulation.Then transmission system model of 16DPASK is established.Simulation results show that the spectrum width of 16DPASK is one quarter of that of BASK.Both the chromatic dispersion and nonlinear tolerances of phase tributary are larger than that of amplitude tributary.