Abstract: A driver model which is used to simulate the behavior of driver obstacle avoidance under two different states of mind was to be established. According to the characteristics of crossover model between driver and vehicle, PID (proportion integration differentiation) control rule and time delay were used to express the driver trajectory dynamic model. A model of vehicle dynamic with two degrees of freedom was built and some parameters were set to construct the driver model. Finally CarSim vehicle simulation software was applied to simulate the driving behaviour and reaction of driver under different states of mind. The result of study showed that both the delay of reaction time and obstacle avoidance behavior of human were different when the drivers were under different states of mind. Therefore, the developed driver model matched with the actual mental state of drivers, and the results will lay the foundation for future research which is to develop a control algorithm for a driver obstacle avoidance assistance system.