Objective To investigate the effect and possible mechanism of pretreatment of Fumai decoction on the incidence of arrhythmia in rat myocardial ischemia model and the expression of Cx43. Methods SD male rats of myocardial ischemia model were induced by left anterior descending ligation. The continuous electrocardiographic was monitored for one hour to observe the effect of pretreatment of Fumai decoction and the arrhythmia score. The Cx43 expression was characterized by Westernblot. Results（1）Evaluation of arrhythmia：after myocardial ischemia models were induced， all the groups responded in arrhythmia， but with different degrees. The incidence of arrhythmia in model group was 87. 5%. The incidence of arrhythmia in low dose， middle dose and high dose groups of Fumai decoction were 62.5%， 50.0%， 62.5%， respectively. Compared the arrhythmia score， all the three groups of Fumai decoction was lower than the model group（P<0.05）. （2）Expression of Cx43：ham operation group showed the highest relative expression of Cx43/GAPDH and higher than the model group（P<0.01）. High dose groups of Fumai decoction was significantly higher than model group（P<0.01）， which was similar to tartaric acid metoprolol group. Low dose and middle dose of Fumai decoction were higher than model group（P<0.05）， while the three groups of Fumai decotion showed no statistical difference（P>0.05）. Conclusion Pretreatment of Fumai decoction can reduce the incidence of arrhythmia in myocardial ischemia model induced by left anterior descending ligation and increase the relative expression of Cx43/GAPDH. This might be the result of improving the myocardial tissue blood flow and oxygen supply to improve the expression of Cx43， reduce the occurrence of arrhythmia.