Abstract: The foundation of large storage tanks has requirements of large bearing capacity and limited differential settlement. Because the natural foundation generally cannot meet the requirements of bearing capacity and deformation, it needs to be treated. It is revealed that the settlement distribution of the foundation of storage tanks has the shape of the disc with large settlement inside and small one outside, and the settlement within the scope of 0.7R away from the center of foundation is large and has no great change（about 20%）through field tests and numerical simulations, which is defined as the core area for the foundation settlement of storage tanks. The most sensitive influencing factor to the settlement of CFG pile composite foundation of large storage tanks is the length of CFG piles. On this basis, the spatial variable rigidity design method with equilibrium settlement for the composite foundation of large storage tanks is proposed to raise the rigidity in the core settlement areas and to reduce that of the foundation in other areas. Thus the differential settlement of tank foundation is effectively reduced and the stress state of storage tank structure is improved.