Abstract: Primary percutaneous coronary interventions (PCI) is the best available reperfusion strategy for patients with acute coronary syndrome (ACS) but despite re-establishing the epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue. Studies have shown that 5% to 50% of patients undergoing PCI recanalization therapy have slow flow and no reflow (NR/SF) phenomenon. Some methods, such as intracoronary adenosion, intracoronary nitroprusside, intracoronary verapamil or tirofiban, ischaemic post-conditioning, thrombus aspiration or distal filters, have been used for prevention or treatment of NR/SF. But so far, no drug or device can completely prevent NR/SF. In recent years, more attention has been paid to nicorandil for it can improve the micro-circulation of the myocardium. In this article, we review the beneficial effects of niconrandil for NO-Reflow phenomenon in ACS patients during PCI and its prognostic significance.