OBJECTIVES: Myasthenia Gravis (MG) is an auto immune disease of neuromuscular junction, which leads to muscle weakness and influences patients’ quality of life (QoL). Treatments for MG patients include thymectomy, acetylcholinesterase inhibitors and immunosuppressant drugs. But in China, Chinese herb is widely used. This study is to prove Chinese herb’s efficacy on treating MG patients. METHODS: The data is performed on a random double blind clinical trial. Consecutive MG patients are enrolled in three hospitals in China, from July, 2008 to June, 2010. Patients (14≤age≤75 years) with class I, IIa, or IIb MG according to Osserman’s classification are enrolled, and are blindly separated into Chinese herb group and control group. The Chinese herb group is treated with Huangqi formula and control group with placebo, treatment duration is four weeks. Muscle weakness is assessed by Chinese Score for MG (CSMG; rang 12-60; higher scores worse weakness), and QoL is assessed by the SF-36 (rang: 0-100; higher scores better QoL); Both CSMG and SF-36 are evaluated at the enrollment and after four-week treatment. RESULTS: Analysis is based on 248 patients (male 110, 44%; age:46±18 year), of whom 125 patients randomized into the Chinese herb group and 121 finish the treatment; 123 in the control group and 120 finish the study. There is no significant difference in demographic and clinical characteristics between two groups (P>0.05), and no difference in CSMG (Chinese herb vs control groups: 24.1±5.9 vs 23.3±6.6) and SF-36 (55.7±16.6 vs 57.7±16.5) at the baseline either. After four-week treatment, muscle weakness declined 6.4±5.0 in Chinese herb group and 1.0±3.8 in control group (P=0.000). However, no significant changes are found in SF-36 scores between the two groups (56.7±16.1 and 57.1±15.9). CONCLUSIONS: This study proves that Chinese herb can relieve MG patients’ muscle weakness, but it is not enough to improve patients’ QoL in four weeks.