Objective To determine the best interventional time of α7nAChR agonist postconditioning that can attenuate myocardial ischemia reperfusion injury cardioprotection in rat in vivo model. Methods Sixty SD rats were randomly divided into six groups（n=10 in each group）: sham group（S group）, ischemia reperfusion group（IR group）, α7nAChR agonist postconditioning at onset of reperfusion group（P0 group）, α7nAChR agonist postconditioning at 30, 60 and 90 min of reperfusion group（P30, P60 and P90 groups）. Serum concentrations of TnI, TNF-α and HMGB1 were assayed at 180min after reperfusion. At the end of experiment, infarction sizes were assessed from excised hearts by Evans blue and triphenyltetrazolium chloride（TTC） staining. Results The infarct sizes (IS%) were 78.4±16.1% in IR group, 60.4±7.0% in P0 group, 48.9±17.1% in P30 group, 54.0±11.8% in P60 group and 63.8±15.3% in P90 group, respectively. Serum concentrations of InI were 1.02±0.12, 0.17±0.04, 0.16±0.02, 0.19±0.04 and 0.14±0.03ng/ml in these groups respectively. As compared to the S group, serum concentration of TNF-α in the IR and P30 groups significantly increased, TNF-α in the P group significantly reduced. Serum concentration of HMGB1 was significantly higher in the IR group than in the S group, but that of all α7nAChR agonist postconditioning groups was significantly lower. As compared to the IR group, infarct size and serum concentrations of TnI, TNF-α and HMGB1 in all α7nAChR agonist postconditioning groups significantly reduced. As compared to the P0 group, serum concentrations of TNF-α and HMGB1 in the P30, P60 and P90 groups significantly increased. As compared to the P90 group, in the P30 group, serum concentrations of TNF-α and HMGB1 significantly increased and infarct size significantly decreased. Conclusions In rat in vivo models of myocardial ischemia reperfusion injury, α7nAChR agonist postconditioning exerted at 30 min of reperfusion could produce the strongest cardioprotection.