Abstract: Objective :To investigated the feasible dose and the recovery degree of non-depolarized muscle relaxant atracurium in the patients with thymoma combining myasthenia gravis during anesthesia course. Methods :Twenty-seven patients were selected and divided into two groups at random. Group I was the trial group, in which 13 cases had obvious myasthenia gravis symptom. These pabents received ant〔cholinesterase drug orally and hormone treatment before operation. In operation room atracurium O.5mg/kg was injected in vein under the muscle relaxant monitoring and the time for the 4 trains to disappear thoroughly was recorded, 500n after atracurium 0.2mg/kg was injected in vein to maintain the muscle relaxed. Neostigmine was injected in vein to suppress the relaxed muscle after operation. Group II was the control group, in which 14 cases had no myasthenia gravis symptom. Results :In group I,the onset time was 1 min 50 s and the holding time was about 25 to 35 min, after atracurium was injected in vein. In group II,the onset time was 2 min 5 s and the holding time was 20 to 30 min. For those whose musclelax was fairly completed, the rate was 96% to 98% in group I and 80% to 90% in group II .In group I,neostigmine O.O5mg/kg and atropine 0.02mg/kg were injected in vein respectively, antagnize the remnant effect of muscle-relax after operation. If the effect was not obvious, the same dose of neostigmine and atropine were of neostigmine and atropinere used and the ratio ofgiven 10 min later. In group II, the same T4/T1 amounted to 0.75 within 10 min, dose thus meeting the requirementplication of hormone and of extubation. It is not necessary to administrate again. Conclusions :on controlling the symptom and improving the general condition of the body. Though the anticholinesterase drug therapy has been used before operation, it fails to decrease the sensibitity of atracurium obviously. In addtion, it needs careful monitoring for use of neostigmine to antagnize the muscle relax, and increase the dosage according to circumstance to achieve complete recovery of the mus- cular strength, thus ensuring the patients's safety.