Abstract： Objective To investigate the characteristics of electrocardiogram changes during nocturnal asymptomatic hypoglycemia in type 2 diabetes mellitus(T2DM)patients and early diagnosis of cardiac autonomic neuropathy(CAN).Methods A total of 150 patients with T2DM who were admitted to our hospital from June 2015 to June 2022 were retrospectively selected and given 72 h dynamic blood glucose and dynamic electrocardiogram monitoring.According to whether asymptomatic hypoglycemia occurred at night,they were divided into hypoglycemia group(n=62)and non-hypoglycemia group(n=88).According to the Ewing experiment,150 T2DM patients with T2DM were divided into T2DM group(n=90)and CAN group(n=60).Results Compared with the non hypoglycemic group,the hypoglycemic group had an increase in DM duration,LF/HF(P<0.05),HbA1c,average blood glucose,collected heart rate deceleration force(DC),QT dispersion(QTD),end of peak T value(Tp-e),Tp-e/QT,percentage of beats with a difference of more than 50 ms between adjacent normal RR intervals(pNN50),root mean square difference between adjacent normal RR intervals(rMSSD),standard deviation of 24-hour normal sinus RR interval(SDNN),and standard deviation of mean normal RR interval every 5 minutes(SDANN)and the average heart rate decreased within 24 hours decreased(P<0.05).Logistic regression analysis showed that the duration of DM was a risk factor for CAN in T2DM patients,and DC,QTD,and pNN50 were protective factors for CAN in T2DM patients.The characteristic curve analysis of the participants showed that the area under the curve for predicting CAN was 0.811,0.842,0.786,0.801,and 0.886 for the DM duration,DC,QTD and pNN50 respectively.The combined diagnostic performance of these four items was the best.After internal verification,it was found that the model has good discrimination and accuracy.Conclusion T2DM patients with nocturnal asymptomatic hypoglycemia may exhibit elevated,ECG LF/HF and decreased DC,QTD,Tp-e,Tp-e/QT,pNN50,rMSSD,SDNN,SDANN,and 24-hour average heart rate decrease;DM duration,DC,QTD and pNN50 can serve as effective indicators for early diagnosis of CAN in T2DM patients.