Aim To investigate the effects of different doses of simvastatin on plasma activity of tissue factor(TF) and level of tissue factor pathway inhibitor(TFPI) in patients with acute coronary syndromes(ACS).Methods A total of 88 patients with acute coronary syndromes were randomized in to three groups: control group without use of statin,group with 20 mg and group with 40 mg simvastatin therapy.The plasma activity of TF and level of TFPI were measured using IMUBIND~R enzyme-linked immunosorbent assay(ELISA) kit.Results Both doses of simvastatin therapy can significantly decrease the activity of TF(from 0.47±0.58 IU/L to 0.20±0.30 IU/L and from 0.59±0.77 IU/L to 0.36±0.55 IU/L,respectively)(p<0.05),only large dose of simvastatin(40 mg group) can increase TFPI level(from 263±203 μg/L to 369±279 μg/L)(p<0.05).Conclusions Simvastatin can change plasma activity of TF and level of TFPI and may have antithrombotic effect.