The invention specifically relates to a substrate integrated waveguide type wireless passive gas sensor based on LTCC and a preparation method thereof, belonging to the technical field of gas sensing.The gas sensor provided by the invention overcomes the problems of usage of a wired connection manner, inconvenient installation, short service cycle and the like of conventional gas sensors. The gassensor provided by the invention comprises an upper-surface metal layer, a lower-surface metal layer and a LTCC alumina ceramic chip arranged at the middle part, wherein the upper-surface metal layer, the lower-surface metal layer and the LTCC alumina ceramic chip compose a substrate, and the periphery of the substrate is provided with a circle of sidewall metallic cylindrical through holes of asubstrate integrated waveguide, thereby forming a substrate integrated waveguide structure; the sidewall metallic cylindrical through holes of the substrate integrated waveguide are filled with silverpaste; the middle part of the substrate is provided with a gas-sensitive structure; and a slot antenna is arranged on the surface of the upper-surface metal layer. The substrate integrated waveguidetype wireless passive gas sensor provided by the invention makes full use of the advantages of high quality factor, low loss and the like of a substrate integrated waveguide resonator and can effectively increase the distance of wireless testing.