This paper presented a novel approach to objective assessment of facial nerve paralysis based on infrared thermography and formal concept analysis. Sixty five patients with facial nerve paralysis on one side were included in the study. The facial temperature distribution images of these 65 patients were captured by infrared thermography every five days during one-month period. First, the facial thermal images were pre-processed to identify six potential regions of bilateral symmetry by using image segmentation techniques. Then, the temperature differences on the left and right sides of the facial regions were extracted and analyzed. Finally, the authors explored the relationships between the statistical averages of those temperature differences and the House-Brackmann score for objective assessment degree of nerve damage in a facial nerve paralysis by using formal concept analysis. The results showed that the facial temperature distribution of patients with facial nerve paralysis exhibited a contralateral asymmetry, and the bilateral temperature differences of the facial regions were greater than 0.2 ℃, whereas in normal healthy individuals these temperature differences were less than 0.2 ℃. Spearman correlation coefficient between the bilateral temperature differences of the facial regions and the degree of facial nerve damage was an average of 0.508, which was statistically significant (p<0.05). Furthermore, if one of the temperature differences of bilateral symmetry on facial regions was greater than 0.2 ℃, and all were less than 0.5 ℃, facial nerve paralysis could be determined as for the mild to moderate; if one of the temperature differences of bilateral symmetry was greater than 0.5 ℃, facial nerve paralysis could be determined as for serious. In conclusion, this paper presents an automated technique for the computerized analysis of thermal images to objectively assess facial nerve related thermal dysfunction by using formal concept analysis theory, which may benefit the clinical diagnosis and treatment of facial nerve paralysis.