The main purpose of this paper is to select a design variable that can maintain a stable current collection despite changes of span lengths during operation. For the purpose of improving the current collection of the pantograph system, we used a robust design method with tools to select an optimal design variable. As the robust design requires a simulation of selected factors based on the tables of an orthogonal array, it is necessary to configure a numerical model for analyzing a pantograph system. In this study, we induced an equation of motion by implementing a linear 3DOF model in terms of system interpretation. Then, we figured out a time varying stiffness of catenary within a given speed range by configuring a finite element model of the catenary system, and analyzed the contact force by span and speed. Then, we intended to select an optimal combination of design variables that can improve the current collection while high-speed trains are driving. To that end, we came to utilize the robust design method as a kind of optimization technique. Robust design includes the array of signal factors and control factors onto the tables of an orthogonal array and analyzes an S/N ratio and sensitivity as a result of output response characteristics for each design variable level. According to these results, we selected an optimal level of design variables that are likely to improve the current collection. Consequently, we conducted a simulation on selected design variables to check if they have an effect on reducing vibration. By doing so, we managed to confirm their reproducibility.