Aim To investigate the predictive value of D-dimer/fibrinogen ratio (DFR) for slow flow/no-reflow (SF/NRF) during percutaneous coronary intervention (PCI) in elderly patients with acute ST-segment elevation myocardial infarction (STEMI). Methods A retrospective analysis of 240 elderly patients with STEMI who underwent emergency PCI was performed, and the patients were divided into SF/NRF group (42 cases) and non-SF/NRF group (198 cases) according to postoperative distal coronary blood flow. The baseline data, intervention-related indicators, DFR, etc. of the two groups of patients were compared. The influencing factors of SF/NRF and the predictive value of DFR for SF/NRF were analyzed. Results Cardiac function Killip grade 2～3, peak value of creatine kinase isoenzyme MB, peak value of cardiac troponin I, D-dimer, fibrinogen and DFR in SF/NRF group were significantly higher than those in non-SF/NRF group (P＜0.05). The time from symptom onset to first electrocardiogram in the SF/NRF group was significantly longer than that in the non-SF/NRF group, and the preoperative TIMI blood flow grade 0 proportion was significantly higher than that in the non-SF/NRF group (P＜0.05), while invasive systolic blood pressure, invasive diastolic blood pressure were significantly lower than those in the non-SF/NRF group (P＜0.05). Multivariate regression analysis showed that the time from symptom onset to first electrocardiogram and DFR were independent predictors of SF/NRF. ROC curve analysis showed that when DFR＞0.28, the predictive value of DFR for SF/NRF was higher, the area under curve was 0.818 (95%CI 0.763～0.864, P＜0.01), the sensitivity was 73.81%, and the specificity was 75.76%. Conclusion DFR has high predictive value for the occurrence of SF/NRF during PCI in elderly STEMI patients.