Remote Ischemic preconditioning (RIPC) has been reported to improve myocardial microcirculation, promote collateral circulation recruitment, and improve myocardial perfusion in patients.Two large randomized controlled trials demonstrated a perioperative cardioprotective effect of RIPC (reduced troponin levels), but did not find that a single preoperative RIPC improved long-term outcomes of coronary artery bypass grafting(CABG).The effect of a single RIPC before CABG may be too short. This study aims to investigate whether long-term RIPC improved myocardial perfusion in patients 3 months and 6 months after CABG surgery , and to detect changes in blood vascular endothelial growth factor, Nitrc Oxide, adenosine，and Endothelin-1, and to observe MACCE event rates at 12 months.