Objective: Our aimed to evaluate efficacy and safety of intracoronary autologous bone morrow mesenchymal stem cells (BM-MSCs) transplantation in patients with ST-segment elevation myocardial infarction(STEMI). Methods: In this randomised, single-blind, controlled trial, patients with STEMI (aged 39-76 years) were enrolled at 6 centers in Beijing (the People's Liberation Army Navy General Hospital, Beijing Armed Police General Hospital, Chinese People's Liberation Army General Hospital, Beijing Huaxin Hospital, Beijing Tongren Hospital, Beijing Chaoyang Hospital West Hospital). Patients underwent optimum medical treatment and percutaneous coronary intervention,and were randomly assigned in a 1:1 ratio to BM-MSCs group or control group. The primary endpoint was change of myocardial viability at 6 months' follow-up and left-ventricular (LV) function at 12 months' follow-up.The secondary endpoints were incidence of cardiovascular event, total mortality and adverse event at 12 months' follow-up. The myocardial viability assessed by single- photon emission tomography (SPECT). The left ventricular ejection fraction was used to assess LV function. All patients underwent dynamic ECG and laboratory evaluations. This trial is registered with ClinicalTrails.gov, number NCT04421274. Results: Between March , 2008, and July , 2010, 43 patients were randomly assigned to BM-MSCs group (n=21)or control group(n=22) and followed up for 12 months. LV ejection fraction increased from baseline to 12 months in the BM-MSCs group and control group ( mean baseline-adjusted BM-MSCs treatment differences in LV ejection fraction 4.8% (SD 9.0) and mean baseline-adjusted control group treatment differences in LV ejection fraction 5.8% (SD 6.04) ). After 6 months of follow-up, there was no significant improvement in myocardial metabolic activity in the BM-MSCs group before and after transplantation. however,there was no statistically significant difference between the two groups in the change of LV ejection fraction (p=0.30) and myocardial metabolic activity(p>0.05). We noticed that ,after 12 months of follow-up, except for 1 death and 1 coronary microvascular embolism in the BM-MSCs group, no other events occurred and Alanine transaminase(ALT) and C-reactive protein(CRP) in BM-MSCs group were significantly lower than that in control group. Conclusions: It is unreasonable to speculate that intracoronary transfer of autologous bone marrow MSCs could augment recovery of LV function and myocardial viability after acute myocardial infarction.Trial registration: clinicaltrials,NCT04421274. Registered 06,08,2020- Retrospectively registered, https://register.clinicaltrials.gov/NCT04421274.