Abstract: With the rapid development and wide applications of modern wireless systems, such as the wireless communication and radar imaging, much more demands have been proposed for the antenna which is the key component of the wireless system. The shared-aperture antennas integrate multiple antennas with different frequency-bands or different functions in the same radiation aperture. By rationally arranging the antenna units within a limited radiation aperture, the aperture efficiency is significantly improved, and good isolation between different antennas can be achieved to ensure that each antenna works independently. According to the distribution of radiation apertures, the design methods of shared-aperture antennas can be classified as: nested technology, interlaced technology and reuse technology. Compared with the three-dimensional shared-aperture antenna, the planar shared-aperture antenna has the advantages of small size, light weight, low cost, and easy integration. This paper reviews the research progress of microwave and millimeter-wave planar shared-aperture antennas, especially focuses on the millimeter-wave planar shared-aperture antennas based on interlaced technology and reusing technology. Finally, the technologies of shared-aperture antenna are prospected.