Abstract-In this paper, we will propose a new structure for a socket contactor applied to the lead-frame test board. This structure contains a variable open stub to match the impedance of the package and the load board. Its electrical property is considered superior to a conventional spring probe's, especially when it is applied to a QFP device. We will present its equivalent model and discuss this in detail. Note that the transmission line model we use is at this point a substitute for a physical structure. First, its RLC model will be constructed after we demonstrate its simulation and test data. Finally, we will use the MonteCarlo Method to analyze length inaccuracies in manufacturing and observe how this new structure works.