Myasthenia gravis is mainly ruled out by clinical symptoms and signs, auxiliary examination and drug efficacy. 1. Clinical symptoms and signs: Myasthenia gravis is mainly manifested as weakness or even paralysis after continuous muscle contraction, which is usually aggravated in the afternoon or evening due to muscle exertion, and alleviated after rest in the morning, and the common symptoms include ptosis, diplopia, weakness of limbs, choking on drinking water, etc. If it does not meet the characteristics of aggravation after activity, it does not support the diagnosis of myasthenia gravis. If it does not meet the characteristics of aggravation after activity, morning lightness and twilight heaviness, it does not support the diagnosis of myasthenia gravis. 2. Auxiliary examination: Generally, the diagnosis can be further clarified by repetitive nerve electrical stimulation, single-fiber electromyography, chest CT and so on. Repetitive nerve stimulation will suggest high-frequency stimulation with a decremental degree of 30% or more. Single-fiber electromyography suggests tremor widening and blocking. Chest CT may be accompanied by thymoma, etc. If the above features are not met, again the diagnosis of myasthenia gravis is not supported. 3. Drug tests: Fatigue tests and neostigmine tests are mostly positive in patients with myasthenia gravis. Negative results also do not support the diagnosis of myasthenia gravis. If the patient does not meet the above criteria, the diagnosis of myasthenia gravis is not supported. Differentiation from other conditions such as myasthenia gravis syndrome, chronic inflammatory diseases, and botulism should also be considered. The diagnosis and exclusion of myasthenia gravis is complex and should be done under the supervision of a neurologist to avoid any delays.