Abstract: ObjectiveThis meta-analysis aims to determine the optimal timing of invasive therapy in patients with unstable angina and non-ST-elevation myocardial infarction.Methods The following databases are searched,PubMed(1985 to October 2015),The Cochrane Library (January 1975 to October 2015),MEDLINE (January 1980 to September 2015),EMbase (January 1978 to September 2015),CBM (January 1994 to September 2015),CNKI (January 1990 to November 2015),and Wanfang (January 1993 to October 2015).The evaluation of the included studies and data extraction were done by two independent reviewers.Data analyses were performed by using the Cochrane Collaboration's RevMan 5.3 software.Results According to including criteria,seven trials were included finally,of which six were RCTs including 7568 patients,and one was observational study.Meta-analyses showed that the incidence of all-cause death,fatal or non-fatal myocardial infarction at 1 month or long-term follow-up and rehospitalisation related to angina between two groups(<12 h and 12~24 h) were not statistically significant.Similarly,the incidence of all-cause death at 1 month or long-term follow-up between 12~24 h group and >24 h group were not significant statistically(OR=0.99,P=0.96 andOR=0.87,P=0.27,respectively). There was no publication bias among the included studies in terms of all-cause mortality.The incidence of fatal or non-fatal myocardial infarction at 1 month was non-significant(OR=0.71,P=0.20);During the long-term follow-up,the 12~24 h group had a significantly lower incidence of fatal or non-fatal myocardial infarction compared to >24 h group.There was also a reduction in rehospitalization related to angina in the 12~24 h group(OR=0.76,P=0.01).Conclusion For patients with UA/NSTEMI,the potential timing of intervention would be 12~24 h.More studies will be needed to determine the optimal timing for patients with unstable angina or non-ST-elevation myocardial infarction.