Abstract： Objective To investigate relation between atrial enlargement and pathogenesis of atrial tach yarrhythmia.Methods 786 patients were observed with atrial tachyarrhythmia through 24-hour electrocardiographic monitoring,echocardiographic was used to analysis atrial enlargement.Results The patient with left atrial enlargement in atrial tachyarrhythmia was more than those with right atrial enlargement(73.82%vs 21.25%,P＜0,01).Conclusions Atrial enlargement,especially left atrial enlargement,was the one of most important pathogeny in atrial tachyarrhythmia.The enhancement of pressure and muscle tension in atrial were the major factors of electronicphysiobgy disorganization,and the left atrial was the leading position in patients with electronicphysiology abnormity.