Individuals with anxiety disorder often exhibit as imbalance in response to stressors. We sought to explore the relationship between physiological as well as psychological responses under acute mental stress and the severity of the disease. 20 Generalized Anxiety Disorder (GAD) patients (14 males, mean age 46 +/- 10 years) were confronted with the stroop test, during which salivary-alpha-amylase (sAA), salivary cortisol, and heart rate variability (HRV) were assessed. The results showed that stroop test as a stressor induced autonomic nervous response in GAD patients, which was mainly manifested as the increase in HRV representing sympathetic nervous system and the decrease in HRV representing vagal nerve activity. Moreover, the basic function of sympathetic-adrenal medulla system was hyperfunctional in GAD patients while theirs reactivity was limited, which showed the more serious the lesion was, the higher the baseline value of sAA was, and the less sAA secretion increase would be, or even decrease after mental stress. The change of sAA after stroop test in GAD patients can predict the severity of anxiety, but subjective psychological perception can not.