Abstract: Damping coefficient of pile-soil interaction was systematically researched by laboratory test.In the test practical boundary condition was simulated and low-strain reflected wave method was used.It was shown that damping coefficient increased with increasing stress of soil around pile and was influenced by soil property and water content.Among three typical soils: sand,silt and silty clay,damp in silty clay was maximum,that in sand was minimum and that in silt was between the former two under the same soil stress.And damp in saturated soil was larger than that in unsaturated one.Finally,dependency relation between damping coefficient and stress of soil was established by fitting.