The present invention is related with the two-channel point-diffraction interferometer for testing the optical systems or optical elements. The two-channel point-diffraction interferometer comprising a laser source inducing a linearly polarized laser beam which is divided by a beam splitter to a working channel and to a reference channel whereas the one half of light as working channel is directed from the first collimator to the working collimator by a first single-mode optical fiber to keep polarization of light unchanged, and another half of light as reference channel is directed from the second collimator to the reference collimator by a second single-mode optical fiber to keep polarization of light unchanged.