Abstract: This paper focuses on solving a one-dimensional nonlinear consolidation problem with the complementary algorithm. Firstly, a piecewise linear function is used to fit the compression curve of foundation soil. With a control variable introduced, a unified relationship between the void ratio and the effective stress and complementarities of compression curve are obtained. After the differential equation of one-dimensional nonlinear consolidation derived in detail, which including void ratio and effective stress as variables, the problem of nonlinear consolidation at different stages is translated into a standard linear complementarity model by carrying out the finite difference method combined complementarities of compression curve. Consequently, problem of nonlinear consolidation can be solved by linear solving method with the complementary algorithm embedded in. Then, the method proposed here is validated by contrasting with general iterative method. On the basis, the difference of linear and nonlinear solution and all the factors of nonlinear calculation are investigated. And it is found that complementary model algorithm method is superior to general iterative method in calculation efficiency; and it is easy to carry out when embedding the complementary algorithm into a linear calculation program to compute nonlinear consolidation. Also, with the solution of control variables in complementary model algorithm method, the compression condition of foundation soil can be estimated

Key words: one-dimensional consolidation theory, nonlinear analysis, complementary algorithm, linear complementarity model