In recent years, developing novel ideas for precast foundations has become an important issue in onshore wind turbine foundations to improve construction efficiency and to replace the conventional in-situ casting process. In the precast wind turbine foundation, precast modules are assembled together and maintain the structural integrity through circumferential prestressing tendons and shear key tooth joint, where the performance of shear keyed joints is the most important issues studied here in this study. Based on the recent study and systematic analysis of the shear design methods available, formulae for shear keyed dry joints' shear resistance under slip failure and shear failure states is presented. The influence of shear keyed tooth number, presence of reinforcement and confining stress on the shear capacity of the joints are analyzed. The shear capacity is in proportion to the initial compressive stress at the joint, small confining stress results in slip failure while large one slows down the degree of shear failure. Finally, the behavior checking methods based on slip failure mode and shear failure mode are verified and suggested.