Objective To investigate the potential mechanism of astaxanthin and/or aerobic exercise in relieving D-galactose-induced myocardial aging in rats.Methods Forty SD male rats aged 3 months were randomly divided into five groups， with 8 rats in each group： control group （group C）， aging model group （group D）， aging + astaxanthin group （group DA）， aging + aerobic exercise group （group DE） and aging + astaxanthin + aerobic exercise group （group DAE） .There was no intervention for group C. The other four groups were intraperitoneally injected with 100 mg/kg·d D-galactose. Group DA， DE and DAE were treated with 20 mg/kg·d astaxanthin and/or aerobic exercise at 60% VO₂ max， respectively. The experiment lasted for 6 weeks. Twelve hours after the last training， the rats were sacrificed for heart harvesting. The morphology of the heart tissue was observed under light microscope and the related biochemical indicators were measured.Results The morphology of myocardium in group C was normal. Compared with group C， the myocardial cell in group D showed disorder， fiber rupture and inflammatory cell infiltration. Compared with group D， groups DA， DE and DAE showed improvement， including orderly arrangement of myocardial cells， relieved myocardial fiber rupture and reduction of inflammatory cells， especially in group DAE. and the morphology of myocardial tissue in group DAE was much closer to normal. Compared with group C， the activity of superoxide dismutase （SOD）， γ-glutamate cysteine synthase （γ-GCs） and the expression of sirtuin 1 （SIRT1）， nuclear factor erythroid 2-related factor 2 （Nrf2）， heme oxygenase-1 （HO-1） and B-cell lymphoma-2 （Bcl-2） in myocardium and the ratio of Bcl-2/Bcl-2-associated X （Bax） of group D decreased significantly （P<0.05 or P<0.01）； the apoptosis level， the expression of Bax and the malondialdehyde （MDA） content increased （P<0.05 or P<0.01）. Compared with group D， the expressions of SIRT1， Nrf2 and HO-1 in group DA increased significantly （P<0.05）， while the expression of Bax and the MDA content decreased significantly （P<0.05 or P<0.01）. The activity of SOD and the expressions of SIRT1， HO-1 in group DE increased significantly （P<0.05 or P<0.01）， while the expression of Bax and the MDA content decreased significantly （P<0.05 or P<0.01）. The activity of SOD， γ-GCs， the expressions of SIRT1， Nrf2， HO-1， Bcl-2 and the ratio of Bcl-2/Bax in group DAE increased significantly （P<0.05 or P<0.01）； the apoptosis level， the expression of Bax and the MDA content decreased significantly （P<0.01）. Compared with group DA and DE， the expression of SIRT1， Bcl-2 and the ratio of Bcl-2/Bax in group DAE were increased significantly （P<0.05 or P<0.01）， and the apoptosis level decreased significantly （P<0.05）. Astaxanthin and aerobic exercise had synergistic effect on the apoptosis level， the expression of SIRT1， Bcl-2 and the ratio of Bcl-2/Bax in myocardium.Conclusion Astaxanthin and/or aerobic exercise intervention can alleviate and improve D-galactose-induced oxidative stress， which is achieved by increasing the expression of proteins related to the SIRT1/Nrf2 signaling pathway. It can also reduce the level of cardiomyocyte apoptosis and delay the myocardial aging of rats.