Abstract: Objective To assess the prognostic effect of the change of facial muscle strain in hemifacial spasm (HFS) patients with elastosonography before and after microvascular decompression (MVD). Methods The changes of orbicularis oculi muscle and masseter muscle strain in healthy subjects of control group (n=30) and hemifacial spasm patients of HFS group (n=25, including 10 on the left, 15 on the right according to the site of spasm) who underwent microvascular decompression in Aviation General Hospital from April 2013 to April 2014 were observed by elastosonography on 1st day preoperatively and seven days postoperatively respectively. Results There was no difference in strain ratio of orbicularis oculi muscle between the upper eyelids and the lower ones as well as masseter muscle on left and right in control group. The strain ratio of orbicularis oculi muscle in left and right side in HFS left group had statistical difference in lower eyelid before operation (P=0.003), in both upper and lower lid after operation (P=0.000, P=0.021); The strain ratio of orbicularis oculi muscle in left and right side in HFS right group also had statistical difference in both lower and upper eyelid before operation (P=0.000, P=0.020) and in the upper lid after operation (P=0.005). The strain ratio of HFS group and control group showed significant difference in upper lid and lower lid, not only before MVD but also after MVD. Compared with the control group, there was no difference in the strain ratio of orbicularis oculi muscle in the non-HFS side before and after operation, the left and right side of masseter muscle, and the non-HFS lateral preoperatively and postoperatively in HFS group. Postoperative curative effect:the ratio of complete relief was 12% (3/25), obvious relief was 60% (15/25), incomplete relief was 20% (5/25), and no relief was 8% (2/25). Conclusion It suggests that elastosonography can qualitatively detect the stress of muscle in real-time and measure the change of muscle stress as the ratio of strain which can be the prognostic evaluation method of HFS patients.