OBJECTIVE： To investigate the effects of rosuvastatin on in-stent restenosis in middle-aged patients with acute coronary syndrome（ACS）after percutaneous coronary intervention （PCI）. METHODS： Totally 400 middle-aged ACS patients underwent PCI were selected from Xuchang Central Hospital during Mar. 2016 to Apr. 2017， and then divided into control group and observation group according to random number table， with 200 patients in each group. Both groups were given conventional drugs for secondary prevention of coronary heart disease. Control group were given Clopidogrel hydrogen sulfate tablets 75 mg， once a day+Aspirin enteric-coated tablets 100 mg， once a day+Atorvastatin calcium tablets 20 mg， once at bed time every day orally after PCI. Observation group was given Clopidogrel hydrogen sulfate tablets 75 mg， once a day+Aspirin enteric-coated tablets 100 mg， once a day+Rosuvastatin calcium tablets 10 mg， once at bed time every day orally after PCI. Both groups were treated for consecutive 12 months. The serum levels of TG， TC， LDL-C， hs-CRP and IL-35 were recorded in 2 groups before surgery， 1， 3， 6 and 12 months after surgery； in-stent minimum lumen diameter （MLD） was observed immediately after surgery and 12 months after surgery. The occurrence of in-stent restenosis， major adverse cardiovascular events （MACE） and adverse drug reaction （ADR） were recorded. RESULTS： Totally 14 patients dropped out from control group and 18 from observation group， and 368 patients completed the study. Before surgery and immediately after surgery， there was no statistical significance in the serum levels of TG， TC， LDL-C， hs-CRP IL-35 or MLD （P＞0.05）. One day after surgery， the levels of hs-CRP were increased significantly in 2 groups， compared with before surgery （P＜0.05）. One， three， six and twelve months after surgery， the serum levels of TG， TC， LDL-C and hs-CRP were decreased significantly in 2 groups， while the levels of IL-35 were increased significantly， compared with before surgery； and the serum levels of TG and TC （1 and 3 months after surgery）， LDL-C （3 and 6 months after surgery） and hs-CRP （1 month after surgery） in observation group were significantly lower than control group； the level of IL-35 in observation group （1 month after surgery） was significantly higher than control group （P＜0.05）. Twelve months after surgery， MLDs of 2 groups were decreased significantly， and observation group was significantly higher than control group （P＜0.05）. There was no statistical significance in the incidence of in-stent restenosis or the total incidence of MACE and ADR between 2 groups after surgery （P＞0.05）. CONCLUSIONS： Rosuvastatin can effectively improve the levels of blood lipid and inflammatory factor in meddle-aged patients with ACS after PCI， and its effect is better than that of atorvastatin. The drug can delay in-stent restenosis after PCI in these patients， which is better than the effect of atorvastatin. At the same time， rosuvastatin can not increase the risk of MACE and ADR with good safety.