Orthogonal cascaded liquid crystal polarization grating can realize optical beam large angle-scale deflection, and has broad application prospects in the fields of space laser communication and LiDAR. It need to emit and receive laser at the same time in most application fields, but how to solve the problem of separating emitted light from received light has not been reported. To solve this problem, change of polarization state of outgoing polarization light source after passing through passive liquid crystal polarization grating layer and orthogonal cascade liquid crystal polarization grating was deduced based on the theories of 1/4 wave plate, 1/2 wave plate and liquid crystal deflection grating, the reversibility of the polarization state of the outgoing light and the beam deflection angle was verified. An optical structure which could realize the deflection and separation of transmitted beam and received beam was designed using polarization splitting prism, 1/4 wave plate, 1/2 wave plate and orthogonal cascade liquid crystal polarization grating. A test system was constructed, the test results prove the correctness of the theory and the applicability of the optical structure finally.