Aim To investigate the association between CAG polymorphism sites of MEF2A and severity of coronary artery disease in Han nationality of BeiJINg. Methods Using PCR sequencing method to investigate the genotype of exon 11 of MEF2A of all subjects. Case-control study was used to detect the association of the genotype of 4～8 CAG repeat number with the severity of coronary artery disease. Results In 473 coronary artery disease patients and 303 control individuals,CAG repeat number of exon 11 of MEF2A had polymorphism. Under different heredity mode,there was no significant association between 4～8 CAG repeat number and severity of coronary artery disease. Conclusion The genotype of 4～8 CAG repeat number of the exon 11 of MEF2A gene has no significant association with severity of coronary artery disease in Han nationality of BeiJINg.