【Abstract】 Objective To investigate the effect of estrogenrelated receptor α(ERRα) on cardiomyocytes maturation. Methods Embryonic day of 14.5(E14.5), E17.5, new born (nb), postnatal 2-week (p2w) and postnatal 4-week (p4w) mice were used as experiment subjects. Heart samples were collected. Q-PCR and Western blot methods were used to detect mRNA and protein levels of ERRα, ssTnI, cTnI, αMHC and βMHC. ChIP assay were employed to determine the level of histone acetylation levels in the promoter regions of ssTnI, cTnI, αMHC and βMHC , and the binding levels of ERRα with promoters of those genes. Results Expression levels of ERRα, cTnI and αMHC were increased gradually in heart development and maturation (P＜0.05). Meanwhile, expression levels of ssTnI and βMHC were decreased (P＜0.05). Acetylation levels in promoter region of cTnI was went up as the pattern of its gene expression (P＜0.05). However, acetylation levels in promoter of ssTnI, αMHC and βMHC showed no significant changes among each group (P＞0.05). Binding affinity of ERRα with the promoter of cTnI was increased and reduced in promoter of ssTnI (P＜0.05). Conclusion ERRα regulates TnI isoform switch to promote cardiomyocytes maturation.