Abstract: The application provides a interface light path structure with all polarization-maintaining function. A first polarization-maintaining-transferring device includes a first port, a second port, and a third port, wherein the first port receives a first polarized light output by the polarization beam-splitting device, the second port is connected to the first Faraday rotation mirror, and the third port is connected to a first port of the first polarization-maintaining coupler. A second polarization-maintaining-transferring device includes a first port, a second port, and a third port, wherein the first port receives a second polarized light output by the polarization beam-splitting device, the second port is connected to the second Faraday rotation mirror, and the third port is connected to a second port of the first polarization-maintaining coupler.