In high-speed optical polarization division multiplexed (PDM) coherent transmis sion system,16quadrature amplitude modulation (16QAM) is the most promisin g modulation format and the carrier phase estimation is an important technique to compensate the signal phase distor tion caused by the linewidth of lasers in the transmitter and the receiver.The most commonly used methods in the area are QPSK partitioning algorithm and blind phase search (BPS) algorithm,but they suff er from either high hardware consumption,bad performance or narrow range of application.In this pa per,a 640km transmission experimental platform for 224Gbit/s PDM-16QAM WDM co herent detection is set up.First,the received signal is processed by several phase estimation algorithms based on QPS K partitioning algorithm or BPS algorithm,obtaining the bit error rate (BER) curves,the error vector magnitude (EVM) curves and the computational complexity (CC) analysis tables.Then,a modified al gorithm P_1,3/ML omitting the two-stage processing of points in the intermediate ring of 16QAM c onstellation is proposed, which is based on the trade-off between performance and computational comp lexity.After using the modified algorithm in the phase estimation module of the experimental system for data processing,the results show that the computational complexity is reduced to a factor of 2while the BER and EVM performance remain nearly unchanged.