Objective: To study the effect of cardiac autonomic nerve function on body function and weakness in elderly diabetic patients. Methods: A total of 100 patients diagnosed as diabetic autonomic neuropathy in the endocrine ward of Dalian Friendship Hospital from August 2017 to August 2018 were enrolled. The demographics, clinical data, and Activities of Daily Living (ADL) scale of each patient were recorded, and the Instrument Activities of Daily Living (IADL) and the weak score were used to record heart rate variability in each patient. Aweak score of 5 was used as boundaries. Patients with weak score greater than or equal to 5 were divided into weak group, and those less than 5 were divided into non-weak groups. Each indicators were compared between the two groups. The statistically significant variables were used as covariates, and the weak scores were used as dependent variables to perform direct and indirect Logistic regression analysis of covariates and dependent variables and the receiver operation characteristic (ROC) curve. Results: There were significant differences between the two groups in age, diabetes history, heart rate variability, standard deviation of NN intervals (SDNN), standard deviation of sinus RR interval every 5 min (SDANN), triangle index, ultralow frequency (ULF), very low frequency (VLF), activities of daily living (ADL), instrument activities of daily living (IADL) (t=13.45, U=1700, t=-17.52, t=-18.34, U =1204.00, U=3407.56, t=17.90, t=21.89, t=12.21, P< 0.05). Age, diabetes history, heart rate variability, SDNN, SDANN, triangle index, ULF, VLF, ADL, IADL were independent factors of weakness (B=1.14, 0.98, - 0.46, -0.45, -0.79, 0.57, 0.53, -0.67, -0.79, P<0.05). Age, history of diabetes, SDNN, SDANN, ULF, VLF could affect the weak score by indirectly affecting ADL/IADL (B=0.54/0.23, 0.16/0.07, -0.34/-0.04,, -0.54/-0.03, 0.99/0.21, 0.47/0.22, P< 0.05). SDNN, SDANN and ULF could significantly predict weakness, and the sensitivity values of the Yuedeng index maximum were 98ms, 97ms and 236 ms²/Hz, respectively. Conclusions Week score needs to be assessed in patients with diabetic autonomic neuropathy who have a long history of diabetes, and a DANN greater than 98 ms, a SDANN greater than 97 ms, and a ULF greater than 236 ms²/Hz in the heart rate variability index.