A 29-year-old female patient with hyperthyroidism received methimazole 20 mg once daily according to the doctor′s advice. Her liver function was normal before drug administration. Fourteen days after medication,the results of laboratory test showed that ALT was 122 U/ L,AST 87 U/ L. Methimazole was stopped and liver protection treatment was given. Nine days later,her ALT and AST were 42 U/ L and 35 U/ L,respectively. She received methimazole 10 mg once daily again. On day 9 of remedication,the patient developed rash with pruritus,pain and limitation of activity on the right elbow joint,pain on the bilateral shoulder joints and the knee joints,and laboratory test showed ALT 134 U/ L,and AST 109 U/ L. She was diagnosed as drug induced liver injury,drug rash,and drug related arthritis syndrome. Methimazole was stopped again. The patient received the treatments of antianaphylaxis,liver protection and analgesic. Ten days later,her rash mostly disappeared. Laboratory test showed ALT 36 U/ L and AST 24 U/ L. Her arthralgia was improved slightly,could move intentionally,but activity was limitated occasionally.