The invention belongs to the technical field of microwave antennas, and relates to a design of dual-frequency array antennas. A waveguide slot array and micro-strip slot array dual-frequency common-aperture composite antenna array comprises a high-frequency waveguide slot array (1), a low-frequency micro-strip antenna radiation array (2), a high-frequency waveguide feed structure (3) and a low-frequency micro-strip feed structure (4), wherein end-fire slot antennas are adopted by the low-frequency micro-strip antenna radiation array (2); azimuth power division is achieved with strip lines; a waveguide broadside slot array is adopted by the high-frequency waveguide slot array (1); partition waveguides are fed according to the azimuths; each end-fire slot antenna is located between two adjacent waveguides of the waveguide broadside slot array; and the height, of each end-fire slot antenna, greater than that of the waveguide broadside slot array is 70%-80% wavelength of the high-frequency waveguide slot array (1). The problems of shading, mutual coupling, loss, a grating lobe and the like between the low-frequency antenna and the high-frequency antenna are considered; common-aperture combination of two-band antennas is achieved; and aperture multiplexing of low-frequency and high-frequency antennas can be effectively achieved.