Objective:The changes of heart rate variability frequency domain(HRV-FD) before acupuncture of Shenmen acupoint,during retaining needle and after needle withdrawal were observed to analyze the influence of acupuncture of Shenmen on autonomic nerve function,and to explore its possible therapeutic mechanism.Methods:Seventy subjects lay on their back after taking a rest,and then were connected with the Actiheart electrographic recorder for the observation of HRV-FD parameters 10 min before acupuncture,during retaining needle for 10 min and 10 min after needle withdrawal.HRV-FD parameters included the power of very low frequency(VLF),low frequency(LF) and high frequency(HF),and LF /HF ratio.The changes of HRV-FD parameters were analyzed with short-course record analysis program.Results:The differences of VLF,LF and HG were significant between before acupuncture,during retaining needle and after needle withdrawal(P 0.05 or P 0.01).VLF during retaining needle and after needle withdrawal differed from that before acupuncture(P 0.05 or P 0.01).LF during retaining needle and after needle withdrawal also differed from that before acupuncture(P 0.01).HF during retaining needle differed from that before acupuncture(P 0.01).Conclusion:Acupuncture of Shenmen acupoint can have an effect on autonomic nerve function,which may be one of its therapeutic mechanisms.