Overview: Unilateral vocal paralysis with open position is usually resulted from cetral to peripheral pathology of reverse laryngeal nerve. The causes are usually central nervous injury, post-operative neck or thyroids or mediastinum surgery, internal diseases as tuberculosis, viral infection... Major symptoms are hoarseness, voice loss, exhausted voice. Result of sound analysis is a criteria to diagnose and evaluate of effectiveness oftreatment of unilateral vocal with open position. This method is used in many other countries. Objective: Using sound analysis to: Diagnose voice dysfunctionin unilateral vocal cord paralysis with open position. Evaluate effectiveness of autograft fat injection via endoscopic surgery in voice rehabilitation of unilateral vocal cord paralysis with open position. Method: Clinical trial, performed at ENT Department, Nhan Dan Gia Dinh hospitalfrom August 2012 to December 2013. 45 patients were injected into unilateral paralytic vocal cord via endoscopic surgery, and recorded the voice before and at 1-3 month after surgery. The 'I' vowel in voice records will be analyzed using Praat software for Jitter, Shimmer, HNR index. Result - discussion: All patients show good result after surgery. Before surgery, Jimer, Shinner, HNR indexes are 6 time higher than control group. After surgery, these indexes down 1.5 time compared with before surgery and become close to control group.Improvement of Jitter index is 86.7 percent, of Shimmer index is 86.7 percent and of HNR index is 93.3 percent. Overall result of 3 indexes is at rate of 93.3 percent (42/45 patients). Conclusion: Autograft fat and connective fibers injection into unilateral paralytic vocal cordvia endoscopic surgery is an effective method in vocal rehabilitation, with improvement of all indexes, from vowel pronunciation to Jimer, Shinner, HNR indexes. Recording of voice before and after surgery, sound analizing are objective quantitative criteria in diagnosis and evaluation of effectiveness of a treatment method.