Abstract: Path tracking is one of key technologies for intelligent unmanned vehicles, in which the precise control of steer-by-wire (SBW) system is an important factor affecting the accuracy of path tracking. In order to improve the dynamic response performance of SBW system and the accuracy of path tracking under unknown disturbance, an improved sliding mode control method based on a new reaching law is designed and applied to SBW system. Firstly, the mathematical model of SBW system is established considering model uncertainty, system friction and rack force. Secondly, the design principle of sliding mode reaching law is analyzed and obtained. A new sliding mode reaching law is constructed by designing and adding parameter adjusting function. It can adjust the reaching speed dynamically and its performance in discrete form is compared and analyzed. Finally, an improved sliding mode control method is designed for SBW system. Simulation and test results show that the improved sliding mode control method can optimize the dynamic response performance of SBW system for steering wheel angle, and improve the path tracking accuracy.