Abstract: Soft ground improved by piles was treated as a homogeneous composite material.Consolidation equation for composite ground with undrained penetrating piles was established with consideration of mutual interaction between piles and surrounding soil.An analytical solution for consolidation degree of the composite ground was proposed.The validity of the proposed method was conformed through comparison among the present analytical solution and the finite element analysis and other existing analytical solutions.Consolidation characteristics of this kind of composite ground was investigated.It was shown that,based on the proposed analytical solution,the rate of consolidation of natural ground was much slower than that of the composite ground.The larger the values of replacement ratio and compression modulus ratio between piles and surrounding soil,the larger the rate of consolidation of the composite ground;and the larger the value of improved depth,the slower the rate of consolidation of the composite ground.