Abstract: To overcome the short coming in the studies on dynamicproperties in which the pile is considered as a one-dimensional pole,this paper studies the dynamic properties of a pile in an axis-symmetrymodel. A comparison between the two models shows that the ratio of length to radius of the pile influences theeigenfrequencies of the pile. The pile can be analyzed in onedimensional model when eigenfrequencies of high order are neglected, orfor the first four eigenfrequencies, the pile ratio of length to radiusshould be large than 3. Soil-pile stiffness hasmore influence on the first and second eigenfrequencies of the pile. A method isproposed to calculate soil-pile stiffness by an inverse method with the firstand second eigenfrequencies of the pile, so the pile capacity can be computed.