Abstract: The building of Ningbo Commercial and International Trade Center is composed of one skirt building and two towers with A and B, whose structural height and vertical load both have two fold gaps at least and belong to the highrise multi-towers with large chassis. The method of optimized design of pile foundation stiffness to reduce differential settlement is introduced for the design of multi-towers foundation. The composite pile foundation is considered for tower B which has smaller vertical load, and the settlement coupling caused by the difference of the upper loads and the stiffness should be considered in the design of foundation structure. The results of settlement monitoring indicate that the program is satisfactory, and the measured values are far less than theoretical calculation and the limitation of code.