A novel electrochemiluminescence(ECL) method was developed for the sensitive detection of methimazole based on the fact that in the alkaline medium,the weak ECL signal of luminol could be significantly enhanced by a little amount of methimazole on the surface of graphene modified glass carbon electrode.The effects of reaction medium,graphene dosage,luminol concentration and electrochemical scanning rates on ECL signal of the selected system were investigated.Results showed that under the optimal contions of 8.0 μL of graphene amount,0.01 mol·L-1 of sodium hydroxide,0.7 μmol·L-1 of luminol and 100 mV/s of electrochemical scaning rate,the increased ECL intensity for methimazole was linear in the concentration range of 6.0×10-8-1.0×10-5 mol·L-1 with a detection limit of 2.0×10-8 mol·L-1 and a relative standard deviation(RSD) of 3.5%(c=0.5 μmol·L-1,n=11).The proposed method could be applied in the clinical analysis of methimazole tablets with satisfactory results.