An optical coupling apparatus includes: a coupling and polarization beamsplitter, a phase shifter, a 2×2 adjustable beamsplitter, a photoelectric detector, and a microprocessor. Light in any polarization direction can be coupled from an optical fiber into a waveguide, an extra insertion loss is small, intrinsic insertion losses for light in different polarization directions are the same, a structure is simple, and miniaturization is easy to be implemented.