Objective To investigate the efficacy and safety of tranexamic acid in patients with the age>70 years during off-pump coronary artery bypass grafting (OPCABG). Methods From June 2014 to August 2016, 340 patients undergoing elective OPCABG were included in this study. All the patients were more than 70 years old, among whom 282 were males and 58 were females. According to the random number generation method, the patients were randomly assigned to receive either tranexamic acid (30 mg/kg, infusion time was longer than 30 min after anesthesia induction; n=170) or a placebo (infusion equivalent volume of saline solution; n=170). The primary end point was chest tube drainage 6 h and 24 h postoperatively. The secondary end points were blood transfusion volumes, incidence of various thrombotic events, duration of mechanical ventilation, length of ICU and hospital stay. Results Compared with patients in the placebo group, the patients receiving tranexamic acid had a significant reduction in chest tube drainage at postoperative 6 h (275.6±105.1 ml vs. 459.6±110.2 ml, P<0.001) and 24 h (685.3±202.5 ml vs. 915.9±223.6 ml, P<0.001). There was also a significant reduction in allogeneic red blood cell transfusion (0.80±0.66 U vs. 1.60±1.30 U, P<0.001) and fresh frozen plasma transfusion (166±25 ml vs. 257±30 ml, P<0.001). There were no significant differences in incidence of various thrombotic events, duration of mechanical ventilation, length of ICU and hospital stay between the two groups. Conclusion Tranexamic acid can significantly reduce blood loss and transfusion in elderly patients 6 h and 24 h after OPCABG and the incidence of thrombotic events will not increase.