With the increasing demand of access network bandwidth, 100Gb/s/λ coherent PON has becomes the key of future passive optical network (PON). In this paper, a 100Gb/s/λ homodyne coherent DP-16QAM PON system based on blind phase search (BPS) algorithm is proposed. The system uses pulse-shaped polarization multiplexed (PDM)16QAM signals on the optical line terminal (OLT) side to reduce the symbol rate. On the side of optical network unit (ONU), homodyne coherent detection technology is used to receive signals, and the BPS algorithm is used to process the system phase noise during the digital signal processing (DSP) process. The simulation results show that the system can achieve a power budget of 32.2dB after 20km standard single mode fiber (SSMF) transmission. At the same time, by using the BPS algorithm with a high linewidth tolerance, when the bit error rate BER=10-4, after 20km of fiber transmission , the sensitivity loss of the 10MHz laser line width is only 0.6dB more than that of 0.1MHz, which allows the large linewidth laser to be used on the OLT side of the coherent PON system to reduce system costs.