Abstract: The pile-net composite foundation with large diameter rigid piles is used in the tank for the first time. The design, simulation and optimization of the pile-net composite foundation are discussed. According to the calculation of the rigid pile-net composite foundation, it can substantially reduce the settlement and differential settlement of the tank base. On the basis of the preloading settlement monitoring, it is revealed that the results of three-dimensional finite element method are close to the actual test results. Soil pressure cells are installed on the top of the pile bearing stage and in soil between piles. According to the actual monitoring, the sharing ratio between piles and soil is calculated. Large-diameter rigid pile-net composite foundation, compared to the traditional pile-raft foundation, can save more than 60% of investment and more than 50% of time.