应用参变量变分原理推导了复合模量在弹性及塑性状态下的解析解。该解在土为弹性状态时与目前工程常用的面积加权法结果一致，在土进入塑性状态时，与荷载及上的前后刚度比等因素有关。该方法为复合地基压缩模量的求解提供了一种新的思路，可为工程设计人员提供有益的参考。

The analytical solutions of composite modulus in both elastic and plastic conditions are deduced by applying parametric variational principle. The results show that the solution in elastic condition agrees with that calculated by conventional square-weighted average method, while the solution in plastic condition is related to factors including load and the ratio of soil stiffness in elastic condition to that in plastic condition. The solution provides a new way to calculate modulus of compressibility of composite foundation and is beneficial to engineers.