This study attempted to investigate the characteristics of Phonation Threshold Pressure and Phonation Threshold Airflow of Patients who have Functional voice disorder. 50 subjects participated in study (32 subjects were patients who had functional voice disorders and 20 subjects were normal adults). The PAS (Phonatory aerodynamic system, model 6600, KAY electronics, Inc.) was used to measure the data and to do the analysis. Data from the Phonation Threshold Pressure was measured using voicing efficiency of the PAS protocol. Data from the Phonation Threshold Airflow was measured using Maximum Sustained Phonation of the PAS protocol. Those were used because of the ease of phonation. The results of this study showed that the differences in Phonation Threshold Pressure and Phonation Threshold Airflow between patients who had functional voice disorder and normal adults could be significant index. Patients who had functional voice disorder showed more higher figures than normal adults. These results suggest that Phonation Threshold Pressure and Phonation Threshold Airflow are very useful in diagnosing the voice disorder. The measured data also provided useful information for diagnosing patients with vocal fold diseases.