Abstract: In order to make sure for a smooth transportation system, health monitoring of roadbed without affecting the normal running of the road is necessary, so as to take effective measures before problem appears. As a mature technique, the surface wave method could be used as a no demage detection method. However, detection results for roadbed may be affected significantly by traffic vehicles. The properties of roadbed vibration caused by traffic vehicles for two roads in Dongguan are studied in this paper. As the surface wave velocity is related mainly to roadbed properties within a half wavelength deapth, effects of traffic vehicles depend mainly on a psydeuo wave velocity, a psydeuo wave length (frequency) and a related amplititude. Compared to vibrations caused by a homo-source hammer, vibrations caused by traffic vehicles are multi-source, which will cause a psydeuo increase of wave velocity and a psydeuo wave propogation direction. Thus, traffic vehicles may have a significant effect on the results under a certain noise frequency, a psydeuo wave velocity and an amplititude.