Objective:To explore the closed fog mirror in evaluation of velopharyngeal incompetence. Methods:A self-developed closed fog mirror was and used to evaluate for the velopharyngeal compentence and to determine the extent of velopharyngeal compentence according to the map on the fog mirror from nasal air emission and to grade the velopharyngeal compentence from the shape and size of the fog on the mirror. Then choose the right treatment method: speech therapy or pharyngoplasty. Results:The closed-fog-mirror determined different types of velopharyngeal compentence. Conclusion:The closed fog mirror is simple and objective in evaluation of velopharyngeal incompetence.