Objective: To investigate the clinical characteristics of familial hypercholesterolemia and early-onset acute coronary syndrome (ACS), in order to improve the understanding and diagnosis and treatment of the disease. Methods: We retrospectively studied the clinical data of 2 patients with familial hypercholesterolemia and premature acute coronary syndrome treated in the Department of Cardiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. All patients underwent genetic testing and coronary artery angiography. Results: Two patients were heterozygous familial hypercholesterolemia by gene test. Coronary artery angiography showed that three coronary arteries had serious lesions, which recovered well after drug and surgical treatment. Conclusion: Patients with familial hypercholesterolemia were prone to early onset of acute coronary syndrome, which should be identified, diagnosed and treated as soon as possible.