The invention discloses a polarization-unrelated coherent light access method and system, and relates to the field of the optical access network in an optical fiber communication system. The method comprises the following steps: an optical line terminal OLT preprocesses an original signal, and realizes single side band modulation by utilizing a single-polarization IQ modulator; two sections of optical fiber polarization delay lines divide a single-polarization signal into two paths of dual-polarization signals unrelated to each other, and a downlink optical signal is sent after two paths of dual-polarization signals are combined; an optical network unit ONU mixes the downlink optical signal and the optical carrier, and performs the receiving through a photoelectric detector; an informationsignal and a 0 signal are of an interleaving structure in a time domain frame after preprocessing the original signal; the length difference between two sections of optical fiber polarization delay lines is corresponding to the length of the information signal or the 0 signal in the interleaving structure. The uplink-downlink symmetric and polarization-unrelated optical access network architecture is realized, the realization is simple, and the cost is low.