Abstract: To satisfy the requirement for dual-band high-gain antennas of wireless systems, the design of a dual-band high-gain shared-aperture antenna is presented in this paper. The proposed work hybridizes an X-band Fabry-Perot cavity antenna and a Ka-band folded transmitarray, realizing high-directivity beams at two bands and a aperture reuse efficiency of 100%. Two kinds of unit cells are designed to constitute the aperture layer and the ground layer of the antenna, and they have distinct functions at X- and Ka-bands for the incident electromagnetic wave to satisfy the requirements of the Fabry-Perot cavity antenna and the folded transmitarray. To validate the methodology, an experiment is carried out. A good agreement is observed between the simulated and measured results. The proposed antenna realizes an effective bandwidth (for reflection coefficient ≤ −10 dB and gain variation ≤ 3 dB) from 8.62 to 9.35 GHz at the lower band, and from 24 to 34 GHz at the upper band. Broadside radiation patterns are observed at both bands. The peak gain at two bands is 15.5 dBi and 23.1 dBi, respectively. Due to the merits of wide bandwidths, high gain and 100% aperture reuse efficiency, the proposed design is promising for future wireless communication systems.