Gravity expansion foundation is the primary form of onshore wind turbine foundations. Because the prefabricated foundation is a developing trend for wind power structure system, assembly foundation with combinations of key-tooth joints and prestressing dry connections is proposed for onshore wind turbine system in this paper. To examine the mechanical performance and effect factors of this newprefabricated foundation structure, the stability and load-bearing capacity of typical prefabricated foundation structures are analyzed. Structural response characteristic values of prefabricated foundation structures, including foundation void ratio, steel bar stress levels, and concrete compressive stress, are analyzed. The results showthat the reinforcement of shear key construction is the controlling factor in the stress calculation of steel bars in prefabricated foundation structures.