Researchers believe that cognitive expert systems should be capable of reasoning similar to humans. Cognitive expert systems is the study of human brain behavior or information processing. So, Various models proposed for information processing. In this study, we use a model with three levels of processing. Studies shows that stress can affect the performance, behavior, and emotions. There are many studies to find psychological factors of stress. Besides, the results shows that psychological factors play an important role in creating mental and physiological responses to stress. For instance, Lazarus and Folkman propose that stress occurs when people perceived that the demands from external situations were beyond their coping capacity. This study intends to investigate and simulate the stress on a three-level model of information processing.