Abstract: Self-drilling screw connections between thin steel sheets were tested under shearing forces, and the impacts of the sheet thickness and the screw diameter on the shear behavior of the connections were investigated. It has been indicated that: the obtained three typical failure modes including bearing failure of steel sheets, pull-out failure and shear failure of screw, depend on the ratio between the screw diameter and the thickness of the sheet adjacent to the screw head. The shear resistance of each connection is positively correlated with the sheet thickness and the screw diameter, and the initial stiffness and the ductility of the connections are also related to these two parameters. Elaborated finite element (FE) models for the self-drilling screw connections were developed by introducing the Johnson-Cook damage constitutive model and the linear damage accumulation rule, and by considering the geometric characteristics of screw threads. The developed FE models were validated against the obtained test results, which provide accurate simulations of shear behavior of self-drilling screw connections. By using the calculation formulas for the shear resistance of self-drilling screw connections in the Chinese code GB 50018−2002, a new three-stage simplified mechanical model was proposed herein by considering the impacts of the compressive stiffness of steel sheets and of the shear stiffness of screw, as well as of the multi-screws effect, which has been further verified for accurately predicting the shear force versus deformation relationships of self-drilling screw connections.