Background Low diastolic blood pressure (DBP) was reported to be associated with reduced coronary blood flow,subclinical myocardial damage,and cardiovascular events. The aim of this study was to explore the impact of low DBP on clinical outcomes in patients with ST-elevation myocardial infarction(STEMI)undergo-ing percutaneous coronary intervention(PCI). Methods A total of 1232 patients with STEMI were retrospec-tively enrolled and divided into two groups according to admission DBP level:≥70 mm Hg(n=817)and<70 mm Hg (n=415). The relationship between DBP and in-hospital and 1-year adverse events was evaluated. Results In-hospital death occurred in 2.4％of patients. The in-hospital mortality(5.3％vs. 1.0％,P<0.001)and major adverse clinical events(11.1％vs. 7.5％,P=0.033)were significantly higher in patients with a low DBP. DBP<70 mm Hg was associated with in-hospital death(adjusted odds rate=3.31,95％CI:1.36-8.07,P=0.009). Additional significant indicators included eGFR<60 mL/min/1.73 m2 and intra aorta balloon pump(IABP)treat-ment. Seventy-seven(6.3％)patients died in the one-year follow-up. DBP<70 mm Hg was associated with in-creased risk of 1-year death(8.9％vs. 4.8％,Log-rank=9.9 ,P=0.002). Conclusion Low DBP was associat-ed with increased risk of in-hospital and 1-year adverse prognosis in patients with STEMI undergoing PCI, which could be a tool for risk assessment.