Abstract: Objective To study the mechanism, clinical manifestation and diagnostic strategy of ectopic adrenocorticotropic hormone (ACTH) syndrome who was diagnosed as acute myocardial infraction firstly. Methods Clinical manifestation, laboratory and imaging examination, differential diagnostic strategy of a patient with ectopic ACTH syndrome were analyzed. Results The case was diagnosed as non-ST elevated myocardial infarction (NSTEMI) in other hospital by analyzing the patient's (an aged woman) elevated cardiac enzyme, ECG ST-T changes and clinical symptoms. In our hospital, we found that ACTH elevated severely, and adrenal hyperplasia, pancreas occupying lesion, and multiple metastasis in liver through further diagnosis. Conclusion The EAS should be differential diagnosed in patients with AMI complicated with electrolyte disturbances, which should be diagnosed early.