Objective To investigate the relationship between dynamic electrocardiogram P-wave sign and new-onset atrial fibrillation(NOAF)in patients with acute myocardial infarction(AMI)(AMI-NOAF).Methods Totally 240 patients with AMI admitted to Wuwei Cancer Hospital were examined by dynamic electrocardiogram.P-wave sign pa-rameters and clinical data of holter electrocardiogram were collected.The relationship between P-wave sign and clini-cal parameters of AMI patients was analyzed.The patients were divided into NOAF group and nonoccurrence(non-NOAF)group and multivariate Logistic regression model was used to identify the influencing factors of NOAF occur-rence in AMI.Results Killip Ⅲ-Ⅳ grade minimum P wave duration(Pmin)level was shorter than that of Ⅰ-Ⅱ grade.Maximum P wave duration(Pmax)and P wave dispersion(Pd)level were higher than that of Ⅰ-Ⅱ grade(P<0.05).NOAF occurred in 47 of 240 AMI patients(19.58％).The level of Pmin in NOAF group was lower than that in non-NOAF group,and the level of Pmax and Pd in NOAF group was higher than that in non-NOAF group(P<0.05).The heart rate and the proportion of Killip grade Ⅲ-Ⅳ in NOAF group were higher than those in non-NOAF group(P<0.05).Multivariate Logistic regression analysis showed that Killip Ⅲ-Ⅳ grade,high level of Pmax and Pd were independent risk factors for NOAF in AMI(P<0.05).Conclusions The level of Pmin,Pmax and Pd are correlated with Killip grading in AMI patients.AMI-NOAF patients have abnormal P-wave sign in holter electrocardiogram.The high levels of Pmax and Pd are independent risk factors of AMI and NOAF.