The present invention provides an open-aperture waveguide fed slot antenna including a feeding section on a substrate integrated waveguide, an H-shaped slot, a matched end, and a bottom metal layer. One end of the feeding section is open and connected to the slot, providing energy feeding to the slot. A long side of the center section of the slot is connected to a top metal part of the feeding section. Another side is connected to the matching end. The matching end includes metal which is connected to the slot, the metallic via wall and the bottom metal of the feeding section which is connected to the metallic via wall. The antenna has high gain, wide gain bandwidth, a simple structure, and low processing cost and can be applied to millimeter-wave frequency bands as well as other frequency bands.