Aim To investigate the clinical predictive value of free thyroid hormone (FT4)/free triiodothyronine (FT3) ratio for the risk of all-cause death in hospital in acute myocardial infarction (AMI) patients. Methods The clinical data of AMI patients who underwent coronary angiography or percutaneous coronary intervention (PCI) in the Department of Cardiology of the Second Affiliated Hospital of Dalian Medical University from January 2016 to December 2022 were collected retrospectively, a total of 63 patients with complete medical history and died during hospitalization were selected, 180 AMI patients who did not die during hospitalization in the same period were selected as the control group. Results Age, ST elevation myocardial infarction (STEMI), renal insufficiency, atrial fibrillation, heart rate, KillipⅢ/Ⅳ, multi-vessel disease, cardiac troponin I and brain natriuretic peptide (BNP) in the in-hospital death group were higher than those in the survival group, while ejection fraction (EF) was lower than that in the survival group, the difference was statistically significant (P＜0.05). FT4 and FT4/FT3 ratio in the in-hospital death group was higher than those in the survival group, and the FT3 was lower than that in the survival group, the difference was statistically significant (P＜0.05). Multivariate Logistic regression analysis showed that the FT4/FT3 ratio was associated with the risk of all-cause death in hospital in AMI patients (OR＝1.4,5% CI:1.193～2.850, P＜0. 05). In addition, age, heart rate, KillipⅢ/Ⅳ grade, STEMI, renal insufficiency and low EF were also positively correlated with the risk of all-cause death in hospital in AMI patients (OR＝1.4,1.1,2.7,2.8,4.5,4.407, P＜0.05). The results of the ROC curve analysis showed that the FT4/FT3 ratio (AUC＝0.4,5%CI:0.708～0.839, P＜0.001) predicted the risk of all-death in hospital better than FT4 (AUC＝0.0,5%CI:0.561～0.719, P＝0.001) or FT3 (AUC＝0.9,5%CI:0.647～0.790, P＜0.001) alone. The difference in area under the ROC curve was statistically significant (P＝0.001 and P＝0.042). Conclusions FT4/FT3 ratio is related to the risk of all-cause death in hospital in AMI patients, which can predict the risk of all-cause death in hospital in AMI patients. Compared with FT3 or FT4 alone, FT4/FT3 ratio has better clinical predictive value for all-cause death in hospital in AMI patients.