To　study　the　vibration　induced　by　elevated-road　traffic　and　its　propagation　rules　in　soil,　field　measurements　were　carried　out　in　different　sites.　Large　numbers　of　statistics　indicate　that:　the　ground　vibration　induced　by　elevated　road　traffic　is　vertical　vibration　primarily,　whose　dominant　frequency　ranges　from　5　to　25　Hz.　The　vertical　vibration　do　not　always　attenuate　exponentially　with　the　increasing　distance　from　the　vibration　source　to　the　measurement　location,　for　there　is　a　vibration　amplified　region　at　a　certain　distance　and　the　horizontal　vibration　intensity　follows　a　sine-distribution.　The　ground　vibration　is　related　to　multi-factors　as　the　vehicle　load,　the　vehicle　velocity,　the　international　roughness　index(IRI)　of　the　road,　the　expansion　joint,　the　basement　form,　the　soil　dynamic　performance,　the　wave　cross-section　and　the　vibration　reduction　methods.　The　combination-function　method　which　could　reflect　the　effect　of　the　vibration　amplified　region　and　other　multi-factors　was　proposed　to　forecast　the　Z-direction　vibration　levels.　The　relevant　forecast　fomula　for　Z　vibration　levels　was　given,　which　had　a　better　fitting　effect　than　the　conventional　methods.