Abstract: It is very important to describe the pile-soil interaction accurately and quantitatively in quantitative analysis of pile defects.Simulating the pile-soil interaction with a viscous damper,the pile-soil interaction model experiment and the shear wave velocity experiment of six kinds of saturated soils are performed.The test results show that the consistent relation between soil shear wave velocity and damping coefficient can be established for these saturated soils.The difference between experimental damping coefficient and rational damping coefficient is also analyzed with the results,and the coefficient for correction for rational damping coefficient,which is a function of shear wave velocity,is achieved.With the analytical solution of pile response under longitudinal vibration,the influence of factors on the attenuation rules of velocity wave along pile shaft is studied.The factors include the damping coefficient,the impulse duration and amplitude of transient impact force,and the elastic ratio,density,length,sectional area of piles.With the result,it is confirmed that the only significant factor which influences the attenuation rules of velocity wave is the damping coefficient,and the attenuation rule of velocity wave is obtained.Then,the relational expression is established with the relation between the soil shear wave velocity and the damping coefficient and the energy distributing character at the defect to analyze pile defect quantitatively with soil shear wave velocity and velocity response of pile top.With the expression,the error of determining the damping coefficient with shear wave velocity is analyzed.The results show that most of the final errors in defect degrees are lower than 10% and it is feasible to determine the damping coefficient with shear wave velocity.