Objective:To investigate the characteristics of short-term prognostic factors in very elderly patients with acute coronary syndrome (ACS).Methods:A total of 2 912 ACS patients admitted to Shengjing Hospital of China Medical University from January 1, 2010 to October 31, 2014 and treated with percutaneous coronary intervention (PCI) were enrolled and divided into two groups according to age: very elderly group (≥75 years, 480 cases) and control group (< 75 years, 2 432 cases). The clinical data and coronary artery lesions of the included patients were detected. Major cardiovascular adverse events (MACE) occurred within 30 d after discharge were followed up and recorded. The short-term prognostic factors in very elderly patients with ACS were analyzed by Logistic regression.Results:Compared with control group, the percentage of hypertension, global registry of acute coronary events (GRACE) score, high density lipoprotein cholesterol, N-terminal pro-brain natriuretic peptide, the left main lesion ratio and Gensini score in very elderly group were higher, while the percentage of men, number of smoking, hyperlipidemia proportion, red blood cell count, white blood cell count, blood platelet count, albumin, and long term oral administration of aspirin, clopidogrel, statins, angiotensin receptor inhibitor after discharge were lower, and the differences were statistically significant ( P<0.01 or<0.05). During the follow-up period, the all-cause mortality in very elderly group was higher than that in control group: 2.5%(12/480) vs. 0.9% (21/2 432), and the difference was statistically significant ( P<0.01). Multivariate analysis showed that oral angiotensin converting enzyme inhibitor was a protective factor for elderly ACS patients after discharge ( OR = 0.046, 95% CI 0.006 to 0.383, P = 0.004). The receiver operating characteristic curve analysis showed that Gensini score ≥ 87.75 scores was a threshold value for all-cause mortality. The all-cause mortality ratio in high Gensini score (≥ 87.75 scores) group was higher than that in low Gensini score (<87.75 scores) group: 6.6% (9/137) vs. 0.9% (3/343), and the difference was statistically significant ( P<0.01). Conclusions:Very elderly patients with ACS have their own characteristics from both clinical history and prognostic factors. Patients with Gensini score of ≥ 87.75 scores should be closely observed, and drug treatment during hospitalization should be intensified if necessary. Follow-up should be strengthened for such patients, and oral drug treatment should be continued after discharge.