Homodyne coherent optical communication can achieve very fast communication rate and the quantum limited sensitivity.It is one of the most potential technology in the field of space communication.Taking the narrow line width DFB laser as local oscillator，combined with 90° optical mixing and Costas digital optical phase locked loop technique，optical homodyne coherent reception was realized.The experimental results indicate that after the two lasers transmit through the 90° optical mixing，the phase difference between I branch and Q branch will keep 90° for a long time.Costas digital phase locked loop can lock the phase difference between the two lasers for a long time.By receiving the 2Gbps BPSK optical signal and correcting the output signal with the technique of the baseline recovery technology and magnitude judgment，the baseband signal can be well demodulated.