This study aims to assess the associations of admission systolic blood pressure (SBP) level with spontaneous reperfusion (SR) and long-term prognosis in ST-elevation myocardial infarction (STEMI) patients.Data from 3809 STEMI patients who underwent primary percutaneous coronary intervention within 24 h, as recorded in the Chinese STEMI PPCI Registry (NCT04996901), were analyzed. The primary endpoint was SR, defined as thrombolysis in myocardial infarction grade 2-3 flow of IRA according to emergency angiography. The second endpoint was 2-year all-cause mortality. The association between admission BP and outcomes was evaluated using Logistic regression or Cox proportional hazards models with restricted cubic splines, adjusting for clinical characteristics.Admission SBP rather than diastolic BP was associated with SR after adjustment. Notably, this relationship exhibits a nonlinear pattern. Below 120mmHg, There existed a significant positive correlation between admission SBP and the incidence of SR (adjusted OR per 10-mmHg decrease for SBP ≤ 120 mm Hg: 0.800; 95% CI: 0.706-0.907; p<0.001); whereas above 120mmHg, no further improvement in SR was observed (adjusted OR per 10-mmHg increase for SBP >120 mm Hg: 1.019; 95% CI: 0.958-1.084, p = 0.552). In the analysis of the endpoint event of mortality, patients admitted with SBP ranging from 121 to 150 mmHg exhibited the lowest mortality compared with those SBP ≤ 120mmHg (adjusted HR: 0.653; 95% CI: 0.495-0.862; p = 0.003). In addition, subgroups analysis with Killip class I-II showed SBP ≤ 120mmHg was still associated with increased risk of mortality.The present study revealed admission SBP above 120 mmHg was associated with higher SR,30-d and 2-y survival rate in STEMI patients. The admission SBP could be a marker to provide clinical assessment and treatment.ClinicalTrials.gov (NCT04996901), 07/27/2021.© 2024. The Author(s).