Evaluation of aerodynamic conditions within the glottis is very important to the study of physiology and pathology of voice production. Among the diagnostic modalities currently available, measuring the mean air flow rate(MAFR) is the most widely used method. However, measuring MAFR is not a quite objective method due to its dependency on the sound intensity during the pronounciation of vowels. In order to obtain a more objective air flow rate, in this study the phonation of /pa/ using the phonatory function analyzer was performed three times each to twenty-five patients with voice disorders and twenty-five control patients. And the ratio of maximum air flow rate between /a/ and /p/(AC/DC ratio) was calculated and analyzed for each group. The results showed that there were differences of AC/DC ratio between groups of voice disorders and control, and between groups of vocal polyp and vocal cord palsy. In conclusion, AC/DC ratio obtained during the phonation of /pa/ using the phonatory function analyzer can be useful in differentiating the abnormal phonation among the paitents with hoarseness as well as in predicting the treatment result of the postoperative voice disorder patients by comparing the preoperative and the postoperative AC/DC ratio.