In order to research the relationship between various methods of treatment and their prognosis on Bell's palsy, 164 cases of Bell's Palsy were reviewed. According to the results of ENoG test, 164 cases were divided into three groups A, B1 and B2. Group A: the paretic side ENoG loss was less than 90%, group B1: the ENoG loss was more than 90% and without surgical decompression of facial nerve, group B2: the ENoG loss was more than 90% and with surgical decompression. All of the patients had follow up for 1-3 years or even longer after onset. The grades of recovery of facial function were evaluated by modified classification system as originally proposed by Portmann. The facial function of 77 cases of group A were recovered satisfactorily except 3 patients, the average points were 19.22 +/- 1.18. The average points of group B1 (41 cases) and B2 46 cases were 14.4 +/- 3.49 and 15.4 +/- 2.08 respectively. Comparing the results with group B1, B2 and A, there was no statistical significant difference (P > 0.05) between group B1 and B2, but the results of group A were statistically significant better than group B1 and B2 (P < 0.01). The prognosis of Bell's palsy might mainly depend on the degree of degeneration of facial nerve. A satisfactory recovery can be expected when ENoG test loss was less than 90%. If ENoG loss was more than 90%, neither surgical decompression nor steroids therapy could change the prognosis statistically.