Abstract: The expression levels of 90d, 180d and 270d Landrace cardiac muscle, dorsal muscle and leg muscle were determined by Real-time PCR.Total RNA was extracted from muscle. The MEF2a PCR primers was designed according to blast homologat the conserved regions.β-actin was used as loading controls.The results showed that the cardiac muscle and dorsal muscle mRNA levels were not significantly varied among different day, expect leg muscle (P<0.05). From 90d to 270d, MEF2a expressions level were significant varied among cardiac muscle, dorsal muscle and leg muscle (P<0.05), and the highest is leg muscle, the second is dorsal muscle, the lowest is cardiac muscle. It was deduced that the main function of MEF2a is to promote I myofibrillar formation and not to mediate cell differentiation during adult pig muscle