Using　ray　tracing　technique,　synthetically　considering　the　tunnel　dielectric　constant　and　reflectance,　the　frequency　and　power　of　transceiver,　and　the　gain　of　antennas,　etc,　a　certain　prediction　model　and　simulating　of　the　propagation　of　electromagnetic　wave　in　tunnel　is　built　up,　the　relationship　between　the　transmission　distance　and　the　valid　number　of　multipath,　the　relationship　between　the　transmission　distance　and　single　path　transmission　attenuation　and　time　delay,　and　the　expressions　of　total　power　and　transmission　attenuation　of　multipath　signals　in　three　dimensions　are　deduced.　It　is　the　base　of　the　application　of　anti-decline　technique.　Finally,　by　contrasting　multipath　transmission　simulating　results　and　the　test　results　with　the　similar　situation　it　is　demonstrates　that　the　built　model　is　feasible.