Objective In order to study the effect of Akt on cardiomyocytes proliferation, the expression of Akt during postnatal development of rat heart was detected and the change of mitosis was examined after Akt was activated on cardiomyocytes. Methods The mRNA expression of Akt and the phosphorylation level of Akt protein during the postnatal developmental process (five cases per groups) were detected by RT-PCR and Western blotting analysis in rat hearts. H9c2(2-1) cardiomyocytes were originally isolated and cultured from rat BD1X heart.The Akt was activated by insulin stimulation and/or pCIS2-Akt-WT plasmid transfection. After that the expression of phosphor-histone H3(H3P) protein was detected by immunoprecipitation analysis on H9c2(2-1) cardiomyocytes. Results The mRNA expression of Akt and the phosphorylation level of Akt protein were down-regulated significantly（EM>P/EM><0.01）during postnatal 0-day-old group to 2-week-old group of rat heart. Actived Akt increased markedly the expression of H3P protein on H9c2(2-1) cardiomyocytes（EM>P/EM><0.01）. Conclusion Akt can promote mitosis of