Abstract: In order to evaluate the level of road safety, this paper proposes a synergetic-fluctuating model which is derived from theories of higher Synergetics, population dynamics, and system analysis engineering. In this study, a great deal of field survey data is obtained via a set of physiological and psychological detection devices. By analyzing data combined with driving comfort threshold, a synergetic-fluctuating model is founded according to different effects, caused by traffic factors such as people, vehicles, roads, and environments which are imposed to drivers and induce various psychological responses to drivers. In addition, a real case study, which is maele on the proposed model to evaluate the safety level of mountain two-lane road in China, is presented. Through the case study the rationality and applicability of the model is validated. Thus a new research method for traffic safety and the further measures of improving road safety are provided.