The invention relates to a small broadband substrate integrated waveguide planar magic-T structure, which comprises an upper layer of metal surface, a middle layer of metal surface and a lower layer of metal surface of a dielectric substrate. The dielectric substrate is provided with two rows of parallel metal posts, and a slot line structure etched out from the middle layer of metal surface so as to greatly realize the energy transmission from a microstrip line to substrate integrated waveguide (SIW). The adopted equal power division network of the substrate integrated waveguide (SIW) replaces the traditional branch structure, so that the volume of the whole planar magic-T structure is decreased to a half of the volume of the past substrate integrated waveguide (SIW) planar magic-T structure, the relative bandwidth of work of the magic-T is greatly increased, and the planar magic-T structure has good isolation characteristics with a difference arm and an equal power division port. The small broadband substrate integrated waveguide (SIW) planar magic-T has simple design, small volume and good electrical property and is easy to be integrated with other planar microwave millimeter wave circuits.