Abstract: Provided is a dual-polarization high-isolation Cassegrain antenna, including a main reflector, a secondary reflector and a diagonal horn feed. The diagonal horn feed includes an integrated cross-polarization coupling-structure and a diagonal horn protruding structure, where a hollow part of the diagonal horn protruding structure is diagonal horn-shaped, and a horn opening is upward. An edge line is arranged in the diagonal horn feed, and the edge line passes through the diagonal horn protruding structure and the cross-polarization coupling-structure. The cross-polarization coupling-structure includes a first port and a second port. The second port is located at a side surface of the diagonal horn feed, and an access is communicated with an edge line of a diagonal horn. The first port is located at a bottom surface of the diagonal horn feed.