Objectives：We investigated the significance of interoceptive fear in assessment of panic disorder (PD) patients. Methods：102 patients affected by PDs with (n=68) or without (n=34) agoraphobia according to DSM-IV criteria completed self-report questionnaires, such as Albany Panic and Phobia Questionnaire (APPQ), The Expanded Anxiety Sensitivity Index (ASI-R), Agoraphobic Cognitions Questionnaire (ACQ), Body Sensation Questionnaire (BSQ), Beck Anxiety Inventory (BAI), and Panic Disorder Severity Scale (PDSS). Pearson correlation analysis, stepwise regression analysis, paired t-test and independent t-test were used. Results：All variables except BSQ were significantly correlated with panic severity. In stepwise regression analysis, interoceptive fear and catastrophic cognition were the most significant predicting variables for panic severity. After 3-months medication, all variables significantly diminished, but interoceptive fear and catastrophic cognition of panic patients were still significantly higher than normal control. Conclusion：Interoceptive fear is the fear of automatic sensations that are similar to those of a panic attack and is the most significant variable in predicting panic severity. After 3-months medication, interoceptive fear significantly decreased, but still was higher than the control group.