The invention relates to a horn antenna, in particular to a thin-substrate vibrator difference beam plane horn antenna which comprises a micro-strip feeder line (2), a horn antenna body (3) and vibrators (4), and the micro-strip feeder line (2), the horn antenna body (3) and the vibrators (4) are arranged on a dielectric substrate (1). The horn antenna body (3) is composed of a first metal plane (7), a second metal plane (8) and two rows of metalized via hole horn side walls (9), odd-number metalized via hole arrays (11) and even-number dielectric-loaded waveguides (17) are arranged in the horn antenna body (3), the dielectric-loaded waveguides (17) are connected with the vibrators (4) respectively on the caliber face (10) of the horn antenna body (3), and the vibrators (4) connected with the left half antenna (15) is symmetrical with the vibrators (4) connected with the right half antenna (16). The polarization direction of an antenna radiation field is parallel with the substrate. The antenna can be made through a thin substrate, and is high in gain, large in zero depth, low in cost and compact in structure.