Abstract: Objective To study autonomic nerve function in patients with diabetes mellitus. Methods Time domain and frequency domain methods of heart rate variability (HRV) tests were performed in 120 patients with diabetes mellitus and 120 normal subjects. Results SDNN (75.96 ± 33.78, 147.01 ± 27.66)、SDANN(66.35 ±26.69, 123.48 ±35.07)、 SDNNindex(39. 35 ±23.52, 52.43 ± 16. 67)、 rMSSD(15.91 ±7.55, 34. 99 ± 15.61)、 PNN50(1.62 ±3.12, 10. 41 ±7.35)、 TF(6. 03 ±0. 76, 6. 86 ±0. 63)、 LF(5.25 ±0. 93,5.80 ±0. 75)、 HF(4. 19 ±0. 82,4. 72 ±0. 86)were significantly lower in patients with diabetes mellitus than those in normal subjects (P< 0. 01). Conclusion It is significanthy lower of heart rate variability in patients with diabetes mellitus.