OBJECTIVE： To study the protective effect and mechanism of astragaloside Ⅳ on D-galactose （D-gal）-induced primary cardiomyocytes apoptosis. METHODS： Wistar neonatal rat primary cardiomyocytes were isolated and cultured. The cardiomyocytes were divided into normal control group （DMEM high glucose medium without serum）， D-gal group （DMEM high glucose medium without serum containing 5 g/L D-gal） and astragaloside Ⅳ low-concentration， medium-concentration and high-concentration groups （after cultured with DMEM high glucose medium without serum containing 25， 50， 100 μg/mL astragaloside Ⅳ for 1 h， and then replaced with DMEM high glucose medium without serum containing corresponding concentration of astragaloside Ⅳ and 5 g/L D-gal）. Cardiomyocytes activity was detected by CCK-8 kit after cultured for 48 h. The apoptosis level was detected by Hoechst staining （cultured for 24 h） and flow cytometry （cultured for 48 h）. The mRNA expressions of apoptosis related factors （Bcl-2， Bax， Caspase-3） and ANP in cardiomyocytes were detected by RT-PCR after cultured for 24 h. RESULTS： Compared with normal control group， the activity of cardiomyocytes， mRNA level of Bcl-2 and ratio of Bcl-2/Bax were decreased in D-gal group， while apoptosis rate and mRNA levels of Bax， Caspase-3 and ANP were increased， with statistical significance （P＜0.05 or P＜0.01）. Compared with D-gal group， the activity of cardiomyocytes， mRNA level of Bcl-2 and ratio of Bcl-2/Bax were increased in astragaloside Ⅳ groups， while apoptosis rate and mRNA levels of Bax， Caspase-3 and ANP were decreased， with statistical significance （P＜0.05 or P＜0.01）， and in concentration-dependent manner. CONCLUSIONS： Astragaloside Ⅳ can protect D-gal induced primary cardiomyocytes from apoptosis， the mechanism of which may be associated with the increase of Bcl-2/Bax ratio and the decrease of mRNA expressions of Caspase-3 and ANP.