Automobile steer by wire system (SBW) is a novel steering system. Firstly, the linear four degree of freedom dynamics model with steering torque as the input is built. Then the design ,simulation and multi discipline optimization parameterized platform of SBW is built based on Matlab Graphic User Interface, which can design and simulate steering system performances quickly. Effects of different parameters such as velocity, moment inertia of steering wheel and tire cornering stiffness on handling and stabilities are analyzed. Finally parameters are optimized to minimize the response total variance under torque input and improve the response under steering torque input.