This paper reviews the history, the research approach and research methods of traffic psychology, and presents the basic features of visual perception, risk compensation theory and risk homeostasis theory to explain the traffic behaviors and the driver's attitude change on various road environments. Emperical examples demonstrating the relationship between the driving experience and age, the driving and driver's fatigue and commuting stress are pointed out, and demonstrating the road lighting, the psychological right of way, the communication on the road, the driver's attitude on the traffic law are pointed out in other to understand the traffic behaviors. This paper attempts to identify that the important factor in accident causation is the behavior of traffic participant and identify the traffic psychology can contribute to develop the effective accident countermeasures.